浇灌帷幕孔时，导管端头应下到距孔底（）处。
A.1米
B.1.5米
C.0.5米
参考答案：C
点M（a，0）在______轴上；点N（0，b）在______轴上．
It was only when I reread these poems recently ______ I began to appreciate their beauty.
A．until B．that C．then D．so
