对制种产量有明显影响的是（）。
A.空间隔离
B.时间隔离
C.花期相遇
D.亲本纯度
参考答案：C
－It’s reported that there’s _____ big breakthrough in the cancer treatment.
－If only my son could be brought back to ____ life!
A．a; /
B．/; a
C．the; the
D．a; the
His mother suggested he ______ to see the doctor, because his pale face suggested he ____ ill.
A．would go, had been
B．go, was
C．went, had been
D．must go, was
