什么叫欠超高？
参考答案：
列车速度高，而所设置的超高不足，这个超高不足量叫欠超高。
-- I ________ to your birthday party last Sunday!
-- Unfortunately, you were on business.
A．had come
B．came
C．would come
D．would have come
溶组织内阿米巴的感染阶段是（）
A.滋养体
B.单核包囊
C.双核包囊
D.四核包囊
E.单核包囊和滋养体均可
