China is greatly developing the energy from the sun and wind. These new types of energy cost very little and will never ____.
按要求填空
白色盘状南瓜与黄色球状南瓜杂交,F1全是白色球状南瓜,F2中白色盘状南瓜杂合体有3360株,则F2中纯合的黄色球状南瓜大约有( )
实验室常用下列装置来制取氧气:
-2的相反数是( )