设Ω为曲面x2+y2=2z及平面z=2所围成的空间闭区域，则三重积分的值是()。
A.A
B.B
C.C
D.D
参考答案：C
阴极保护间应在（）设置。
A.泵站内
B.阴极保护汇流点处
C.每100公里处
D.每10个测试桩处
I can still vividly remember to pick our steps in the mountain down the deep valley on my 21 st birthday.()
A. picking.., in the mountains
B. picking ... on the mountain
C. having picked ... from the mountains
D. picking ... from the mountains
的值是()。
的值是()。