What is the answer to the following question :-
A number students want to register for the camp but the number of places
a) is correct. The subject here is "the number of places", not "places"
So it's singular. The number of places "is" limited.
thank you, guys, for your help!
It's worth adding that using the wrong number in the verb (pl rather than s) after 'number' is a very common mistake, even among native speakers. I've heard it, for example, on BBC radio. So don't be surprised if you meet it in real life.