—Jim, your bedroom is so dirty.—Sorry, Mum. I ________ it at once.
— The problem is a bit difficult . — ________ask your teacher for help?
—Did you know that the earth is the home of animals?
—Which country has________population ,China , India or America? — China.
I bought a new sweater last weekend. It________me 120 yuan.
—You must look around when you go________the street.