Miss Zheng always says that it's important for us to _______ the test paper first before we write down the answers.
A：look up
B：look over
C：look through
D：look out
如果水位下降3m，记作-3m，那么水位上升4m，记作（ ）
12
－3=
9
13
____
14
15
16
17
18
19
下列关于人类遗传的叙述中，正确的是（ ）
