Most of the wild animals are_______ because of their bad living environment.
A.in need B.on duty C.at work D.in danger
My son lives a little far from his office, so he always goes to work ________ bus.
Look！Mr. Green is writing ________ the blackboard. How careful he is!
We usually have the first class________ 8：00 in the morning.
More and more young people go skating ________ winter.
We all like watching the TV programme Readers ________ Saturday evening.
