用回声测深仪进行水位观测，站位处水深不得超过50m，观测误差不得大于水深的（）。
A.10%
B.7%
C.5%
D.1%
参考答案：C
严重的 * * 下裂伴隐睾患儿应与下列哪些疾病相鉴别（）
A.肾上腺性征异常症
B.真两性畸形
C.膀胱外翻
D.输尿管囊肿
---Mary, I heard there was an explosion in Luzhou. Could you tell me how it _______?
---Sorry, I don’t know much about it either.
A．came on
B．came about
C．came out
D．came over
