种子休眠
参考答案：
有生活力的种子，由于某些内在因素或外界环境条件的影响，使种子不能发芽或发芽困难的自然现象。
A．It was great. B．what’s the matter C．How about the green one D．Are you free tomorrow E．Thanks, but I am full.
A: How was your trip to Beijing B: ______ I spent four days in Beijing. Every day I did something different.
零件图一般采用（）基本视图表达。
A.主、左两个
B.主、俯、左三个
C.上、下两个
D.上、中、下三个
