Question

Write the correct form: 
1) Listen! Someone (to knock) at the door. 
2) Don't go into the classroom! The students (to write) a dictation there. 
3) They (to discuss) it since five o'clock. 
4) Where is Petrov ? -He (to work) in the library. -He (to work) long ? -Yes, he (to work) since morning.

Answer 1

Извиняюсь, не могу помочь в данном задании