解释强迫休眠的概念
参考答案：
强迫休眠：由于种子得不到发芽所需的条件，暂时不能发芽的现象。
Having mastered the technology of manned spacecraft, China became the third country in the
world ______ manned spaceflight independently.[ ]
A. to develop
B. developing
C. developed
D. develop
离心泵最常用的流量调节方法是改变吸入阀的开度。
