熔化极CO2气体保护焊,中径管垂直固定对接接头盖面层焊接时,最好采用()进行焊接,以便观察熔池。
A.月牙形
B.锯齿形
C.左焊法
D.右焊法
参考答案:D
下列激素中,哪一个不是腺垂体合成和分泌的
A.生长素。
B.催乳素
C.催产素
D.黄体生成素
E.卵泡刺激素
It's certainly hard work. But, ________, a man who wishes to have a career has to make a great many
sacrifices. [ ]
A. on the contrary
B. on the other hand
C. for another
D. in addition