手工电弧焊使用的主要设备有（）、直流电焊机、焊接工具和用具。A、变流电焊机 B、交流

乳牙牙髓病最好发动牙位是()

A．上颌乳切牙，下颌乳磨牙

B．上颌乳切牙，上颌乳磨牙

C．下颌乳切牙，下颌乳磨牙

D．上颌乳尖牙，下颌乳尖牙

E．上、下顷乳磨牙

The two pens are the same, but the red one cost _____________ that one.

A．as much twice as

B．twice as much as

C．much as twice as

D．as twice much as

开放性神经管缺陷可导致羊水 （）

A.AFP降低

B.AFP升高

C.肌酐降低

D.肌酐升高

E.黏多糖沉积

The heavy storm damaged a lot of fruit trees.The fruit prices have _______ immediately.

A．added

B．developed

C．jumped

D．dropped

挤塑机的加温过程，是由（）控制的。