China is greatly developing the energy from the sun and wind. These new types of energy cost very little and will never ____.
NA表示阿伏加德罗常数,下列说法正确的是( )
如图,下列条件中:
(1)∠B+∠BCD=180°;
(2)∠1=∠2;
(3)∠3=∠4;
(4)∠B=∠5.
其中能判定AB∥CD的条件个数有( )
实地距离为200千米,图上距离为20厘米,该图的比例尺为( )