钢板对接仰焊的困难是铁液在重力下产生下垂，极易在焊缝背面产生焊瘤，焊缝正面产生下凹。( )
参考答案：错
"We can't go out in this weather," said Bob, _____ out of the window. [ ]
A. looking
B. to look
C. looked
D. having looked
与幽门螺旋杆菌无关的疾病是（）
A、胃炎
B、反流性食管炎
C、胃溃疡
D、十二指肠溃疡
E、胃癌
