Question

1)You must ... a letter.
A) to write
B) write
C) writing
D) wrote

2) If I (to be) a famous singer, I would travel a lot.
A) was to be
B) will be
C) will
D) were

Answer 1

B You must write a letter
D If I were a famous singer...

Answer 2

You must write a letter.
If I were  a famous singer, I would travel a lot.