问题
选择题
_______,but it is also a great way to lower the number of greenhouse gases in the air.
A．Not only a fun thing is it to do
B．Not only a fun thing to do it is
C．Not only it is a fun thing to do
D．Not only is it a fun thing to do
答案
答案：D
句意：这件事情不但是一件有趣的事，而且是一种降低空气中温室气体的有效途径。否定词位于句首时，应使用部分倒装。
）1个，滑动变阻器1个，电源1个，开关1个，导线适量。请你设计实验证明：电流不变时，电功率与电阻成正比。要求：