Question

When I was at school, we ______ stand up when a teacher came into the classroom.

A. Must
B. shall
C. had to
D. could

Answer 1

I'm going with C. had to.

Step-by-step explanation:

I'm going with C because this answer fits better than the other options.

Answer 2

C.

Step-by-step explanation:

it's simple English learned this in like 3rd grade.