根据句意及汉语提示完成句子，每空词数不限

1._______(即使)you are 50 years old, you should study.

2. When do you________(动身)?

3. Don't________(向……的外面看)the window;look at the blackboard.

4.1 wanted to catch the early train, but I didn't get up_________(及时)．

全世界______有15种鹤，我国就有9种。

A．总

B．共

C．全

D．都