How many students are there in your class? — Forty，and ________ of us are girls.

Do you know Xidan Girl?—Of course. She played _____ guitar and sang song in the 2010 Spring Festival Gala.

Doing exercise for _________ hour every day is good for our health.

will your mother come back? — In two days.

My sister likes playing the guitar, but she can’t play ______.