脊柱过度向前凸出性弯曲,称脊柱前凸,多发生于()
A.颈段脊柱
B.胸段脊柱
C.颈胸段脊柱
D.腰段脊柱
E.骶椎
参考答案:D
若函数f(x,y)在区域D内具有二阶偏导数,则下列结论正确的是( )
A.必有
B.f(x,在D内必可微
C.f(x,在D内必连续
D.以上结论都不成立
According to INCOTERMS 2010, which of the following terms requires the seller to pay for the insurance( )
A.CFR
B.CPT
C.FOB
D.CIP