1.All you have to do is turn on this machine.
What you have to do is be quiet.
The least we can do is send him a pizza on his birthday.
What you musn't do is give them your phone number.
Q.Why do the above sentences use root verb form instead of to infinitive as the complement of be proverb ?
2. I have no other choice _______ to walk to school because I miss the bus.
(1) but (2) than (3) except (4) as
Q. Which is most suitable for the blank ?