造成埋地钢管表面出现凹穴，以至穿孔的主要原因是（）
A.电化学腐蚀
B.化学腐蚀
C.细菌腐蚀
D.生物腐蚀
参考答案：A
When we were young, every evening my brother and I _____stay at home waiting for our mother to come back from work.
A．might
B．would
C．should
D．could
间歇性梗阻表现为
A．肾盂扩张B．初期对肾脏无明显影响C．自截肾D．肾 * * 和肾实质萎缩E．水囊肾
