Answer:
a. possibility
b. past ability
c. promise
d. present ability
e. obligation
f. obligation
Explanation:
a. The use of "may" indicates the possibility of something happening in the future. "May" indicates a higher probability of that happening than "might".
b. "Could have" can indicate past ability or possibility. In this case, it seems that Nina did have the ability or strength to carry the bag, but she didn't do it. "Could have" is commonly used to indicate precisely that - the non-doing of something that we had the ability to do.
c. "Will" refers to a future action that we intend to do. In other words, it indicates a promise, a will to make something happen in the future.
d. "Can", among other things, is used to express present ability. It often accompanies verbs such as "run", "swim", "sing", etc.
e. and f. "Must" and "should" are used to indicate obligation. However, "should" indicates a lighter obligation, closer to a recommendation. "Must", on the other hand, is more imperative.
