One of our rules is that every teacher      wear school uniform while attending the school flag-rising ceremony. 

My sister advised me that I _____ accept the invitation.

Living in a fast-paced world, we                  get left behind if we stop learning.

---Must I hand in my homework now?---No,you__.You can hand it in tomorrow.

–Look! Someone is cutting a tree on the moon.–It _______ be true, Granny. Our teacher says there is no air there.