鲫鱼流出鳃的水与流入鳃的水相比：

在两个密闭容器中，分别充有质量相同的甲、乙两种气体，若它们的温度和密度均相同，试根据甲、乙的摩尔质量（M）关系，判断下列说法正确的是（　　）

I'll buy a dress for my daughter unless I can think of a better idea for a present.

根据句意、释义或中文提示,写出句中所缺单词，使句子通顺。
（1）His parents are angry at his school work. They can't see his ____  (进步)after each exam.
（2）I don't know ____  ( if ) I will have time to join in some activities at school.
（3）Sometimes, I want to ____  (say that you will not do something) to do so much homework.
（4）Orange and yellow are warm colours, they can give you a happy and ____ (满意的) feeling.
（5）Peter is doing an ____  in the laboratory now.