种子的胚由（）构成。
A、胚芽
B、胚根
C、胚轴
D、子叶
E、种皮
参考答案：A, B, C, D
Many people have been ill from a strange disease these days, _____ we’ve never heard of before.
A．it
B．that
C．one
D．this
肺癌根治最常用的标准术式
A．ASB．AIC．TOFD．PSE．MS
