换填法不适用于（）。
A.淤泥
B.湿陷性黄土
C.碎石土
D.杂填土
参考答案：C
简述柑桔春、夏、秋、冬梢的特点及利用。
I received his mother’s telephone call at eleven.＿＿that he was badly hurt in an accident yesterday.
A．Then did I know
B．Only then I knew
C．Only then did I know
D．Only then knew I
