‘is/are’ and ‘do/does’

The original is almost faint praise, best avoided as it is often used as a polite derogative at least in England.
Number one is much better English in my opinion. Number too is too much of a mouth full.

spelt two wrong there... not the best of starts

For the correct sentence in the grammar test, they have a complex sentence in which they have the subject, "Dr Stephens" the verb agreeing with that subject "is" then the object which is comprised of the rest of the sentence. So far it is fine. We then have another clause which makes up the object. We have one of those professors who. We need to delve into latin here to sort this out easily. You have the object (accusative case) which is one, you then have a posessor (genitive case) which is of those professors. Then you have an interesting clause which is indicated by the "who". This is referring to the professors (note the plural) because professors is the antecedant. This means that the subject of the next clause is actually plural meaning the verb, to do, needs to agree with that. The third person plural of "to do" is "they do". So far the sentence given is correct. But when we get to the next 2 possesive cases (genitive) they needs to agree with the subject again because that is what they are linked to. Because the subject is plural, so must be the third person genitive pronoun. This MUST be THEIR. So the correct sentence is number 2 if you are attempting to keep to the original meaning. You should contact the creators of the test and explain all this to them because they are dangerously mistaken.

These are just the ramblings of an extreme pedant and linguist

I hope this cleared it up.

I seem to have been somewhat slacker in my grammar than I should allow, there should be multiple paragraphs there. I just went on much longer than I thought I would.

Thank-you so much DamonTarlaei. Glad you came along and solved my problem. I might just do that and tell the creators of the test about this sentence. I often do that anyway... :)

O.O

Oddly enough, #2 (that I posted) was the correct answer on the test. Someone posted (on that site) that the test said what I put on here.

Well, the important thing is that I know what's correct, anyway.

:D

it's number 2 for sure!!!

According to the rules of American standard English, # 1 is correct. # 2 is not. If you say Dr. Stephens is *one*, you can't use "do" in the sentence. It sounds funny because it's incorrect English. Pretend that the prepositional phrase "of those professors" isn't in the sentence, then see how it sounds.

Dr. Stephens is one who does whatever it takes...
You get the point, right? You must think of the subject as being singular; therefore, you have to use "does" instead of "do".

The reason the first sentence sounds odd to you is that it's incorrect. The following is correct:

"Dr. Stephens is one of those professors who DOES whatever it takes to get his point across to his students."

The noun is not "professors", but "ONE of those professors", which is singular.

Sorry anonymous, you didn't think it through all the way. "One" may be the noun, but "do whatever it takes" is modifying "professors", not "one". Think of it like this:
One what?
One of those professors.
Which professors?
Those who do whatever it takes...
The correct choice is 2 (not the example BEFORE choice 1, because it has a mismatch of case. It should be "get their point across..." not "get his point across...").
This was explained quite clearly in the posts below.

Anonymous (and myself) were right. You can't modify a word in a prepositional phrase, because the prepositional phrase isn't needed in the sentence. It's just added to give extra information. You really don't need to know that Dr. Stephens is "of those professors". The main subject in the sentence is Dr. Stephens. Therefore, the basic sentence is basically "Dr. Stephens=one". Okay, what about him? He does whatever it takes. The fact that he is one among many professors is extra info, which is why they threw it in a prepositional phrase. Once you remember that, you just take the prepositional phrases out of sentences to find the real subject. English 101....

There is an amibguity introduced by the 'who...' clause. As 'who' is unmarked for number, it can refer to either Dr. Stephens, or to 'those professors', and so the answer really is that 'do' and 'does' are both correct!

I can't agree that the antecedent of 'who' is ambiguous. The 'who' is part of the core sentence -- "Dr. Stephens is one who does whatever it takes" ("Dr. Stephens" in the antecedent for the "who"). Inserting the prepositional phrase "of those professors" may create a distraction with its plural object, but shouldn't decrease our certainty about the antecedent. Look at an analogue construction:

"Cosmetic surgery is one of those elective procedures that [isn't/aren't] covered by my insurance policy."

For the sake of simplicity, we can regard the noun clause "Cosmetic surgery is one" as the subject. The predication of such a clause requires a singular inflection of the verb:
"Cosmetic surgery is one that isn't covered by my insurance policy".
The prepositional phrase "of those elective procedures" elaborates on what "one" entails, but isn't part of the subject and doesn't alter the way that the predication of the core sentence needs to be completed.

Seems to me in the cosmetic surgery example that the verb that needs to be inflected is the first is. The second is (isn't/aren't) is part of a phrase that is the object. I feel like "aren't" is actually the better choice here, for the same reason Porsche gave previously: "those (procedures) that aren't covered by my insurance policy". Compare "A face lift is THE one elective procedure that ISN'T covered by my insurance policy".

I think the question hinges on whether, as you suggest, "Cosmetic surgery is one" is the subject or, as I believe, "Cosmetic surgery" is the subject.

Would you rather say:
I am one of those people who has contributed to this discussion
or
.... people who have contributed to this discussion

I am very much in favour of #2, but I am not a native speaker of English.
This is my first post here. Should I introduce myself?

DamonTarlaei: "We need to delve into latin here to sort this out easily."

Let's not. We're not speaking Latin.

Personally I don't see what's wrong with any of these 3 sentences.