Can you tell me the        difference between the words “require” and “request” ? I sometimes get puzzled by their meanings.

It is normal for students to feel_____ before the examination even though they have prepared well.

The bus was due to __________ at 5 p. m.，but it arrived one hour late due to __________ by the heavy fog.

Grandpa is old, but he is still very ____.

— Do you know something about Kwanzaa? — It is _____festival celebrating the culture and history of African Americans.