曲面3x2+y2-z2=27在点(3,1,1)处的法线方程为().
A.
B.
C.
D.
参考答案:B
翟志刚太空第一步,大大激发了国人的自豪感的自信心,培养自己的自尊心和自信心,要寻找个人自尊自信的支点。这个支点是( )
A.正确地认识自己
B.自己突出的优势和长处
C.自己突出的缺点和劣势
D.选择正确恰当的目标
You must be tired now. Why not __________ a rest?[ ]
A. to stop to have
B. to stop having
C. stop to have
D. stop having