焊条电弧焊最基本的操作是（）
A.引弧
B.焊条的摆动
C.运条
D.收尾
参考答案：A, C, D
A．Go along this street to the end. B．Are you feeling better now C．I went to the Palace Museum. D．OK, it’s a piece of cake. E．How far is it
A:______ B:Yes，much better. But I’ve missed so many lessons.
胚的结构包括
①子叶 ②胚芽 ③胚轴 ④胚根 ⑤胚乳 [ ]
A．①②③④
B．①②③⑤
C．①②④
D．①②③④⑤
