I am going over a practice SAT test, and I cannot figure out why one answer is better than another for a particular problem. You are supposed to mark the answer that best replaces the underline portion of the sentence. 11. With billions of tons

Anonymous wrote: When referring to a novel in a paragraph, what is the proper punctuation - do you underline the title only, do you underline and have quotations, do you only have quotations? Also are all the words of the novel's title

Anonymous wrote: I am doing my English homework right now. Normally, on homework like this, I would just sacrifice a few points and guess, but I am absent minded. I did two homework assignments ahead of time, forgot to put them in the binder, and

I am doing my English homework right now. Normally, on homework like this, I would just sacrifice a few points and guess, but I am absent minded. I did two homework assignments ahead of time, forgot to put them in the binder, and now I am down

Yes, it is possible for a noun phrase to have two heads, or more. If "NHS" mrefers to both the clinics and the centres (not just to the clinics) then the head is, as you said, "clinics and centres". I don't know in which way you are asked to go