The sentence where the predicate nominative is correct is D) The best surfers and Mike and she.
Just invert the sentence and you'll know which ones are correct.
She and Mike are the best surfers.
10.A
11.D
12.D
14A
18B
Fix those ones
They are helping verbs. Your helping verbs are the following:
am been may
is can might
are could must
was shall
were should
be will
being would