Answer:
d. both a and b above, but not c
Explanation:
Apostrophes can be used to form possessive case it order to indicate possession; for example:
the neighbours' house
the children's bedroom
the man's car
Besides, apostrophes mark contractions, such as the verb to be and auxiliary verbs like has, have, had and would, in affirmative and negative forms:
Mary's a good student.
I've been to London twice.
She hasn't finished her homework yet.
When I got home, they'd already had dinner.
I'd like a cup of coffee, please.
On the other hand, regular plural forms do not take apostrophe but the suffix -s.
book - books
dog - dogs
memory - memories
