气流超音速流动时，速度分别随断面增大、断面减小而：
A．减小，增大 B．增大，减小 C．不变，不变 D．不确定，减小
参考答案：B
根据句意及首字母提示补全所缺单词。
1. —Are you going to come? —P_______. I'll see how I feel.
2. Don't spit in p________. It's impolite and isn't good for the environment.
3. Tom had a bad cold and he c________ a lot.
4. "Please be quiet. The baby is sleeping," she said in a low v________.
5. As a student, we should obey the rules and can't b________ the rules.
将鼠标指针指向幻灯片中的文本，（）可用于选择文本。
A.单击鼠标左键
B.三击鼠标左键
C.单击鼠标右键
D.双击鼠标右键
