7. 点从点出发，按逆时针方向沿周长为的图形运动一周，两点连线的距离与点走过的路程的函数关系如图，那么点所走的图形是（   ）

A.    B. ,     C.   D. ,

6.若函数的导数是则函数 (0<a<1)的单调递减区间是(   )                                                                                                                                                                                                                                                                      

5.若直线mx+ny=4和圆O:没有交点,则过点(m,n)的直线与椭圆的交点个数为(   )

 A.至多一个         B.2个         C.1个            D.0个

4.甲、乙、丙、丁、戊5人站成一排，要求甲乙均不与丙相邻，不同排法种数有  （  ）

 A. 72            B.54                 C.36            D.24

  C. 且                D. 且

A. 且               B. 且

3.直线与平面满足,,那么必有 (    )

A.          B.                  C.           D.1