若焊条未烘干，焊件坡口留存油污铁锈焊接时易产生（）。
参考答案：气孔
With the increasing unemployment rate, workers who are 50 to 60 years old are usually the first to be___.
A．laid aside
B．laid up
C．laid out
D．laid off
子宫内膜异位症最常见的部位是
A．子宫肌层
B．输卵管
C．卵巢
D．子宫直肠陷凹
E．宫旁韧带
