1번은

Mrs. Snyder received a call from the school that her son _______  classes a lot.

a) has skipped

b) had skipped

c) had been skipping

d ) will have been skipping

여기서 c)가 답이라고 하는데 b)가 불가능 한 이유가 궁급합니다.

2번은

A : Is anyone coming to see you perform at the play?

B : Yes, either my mom or my grandparents _________.

a) is coming

b) is to come

c) are coming

d) are to come

여기는 c)가 답인것은 이해하겠지만 d) 의 be to 용법중 예정으로 쓰면 안되는지 궁급합니다.