单项选择题 21（）

单项选择题 22（）

单项选择题 What is the purpose of building new houses facing north or south

单项选择题 What’s the problem with paper napkins and plastic food wraps

单项选择题 Which is not true about solar heat collector panels

填空题 What is the passage mainly about

单项选择题 Why is insulation required in new houses

单项选择题 What’ s the talk mainly about

填空题 What characteristics can be of a flood

单项选择题 What do we learn about the use of solar energy in the USA

单项选择题 What is the main topic of the lecture

填空题 What does "runoff" mean

填空题 Noise can produce serious ______ stress.

填空题 Noise constitutes a real and present danger to ______ .

填空题 Noise is America’ s most widespread ______ .