Hi everyone

Well, i had a english test today and i have a doubt about one question:
CHILDREN, WRITE YOUR HOMEWORK (it was written exactly like that)
Question: Change this sentence to the imperative.
a) Children, write your homework
b) Write your homework
c) Children writes your homework
d) All wrong
I marked B, but now i guess i was wrong.
Wich is the correct alternative?
Thank you so much. =) xx