—What made Mary so unhappy?
— _ her new necklace. [ ]
A. Losing
B. Lose
C. As she lost
答案:A
下图为玉米种子纵剖面示意图,能为玉米种子萌发提供营养的结构是
A.①
B.②
C.③
D.④
机组运行控制方式有哪几种?