单项选择题22()
A.kindsB.speciesC.sortsD.types
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
单项选择题21()
A.requireB.needC.wantD.lack
单项选择题Why is insulation required in new houses
单项选择题What’ s the talk mainly about
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