8.已知两点 _(1)(4,sqrt (2),1), M2(3,0,2),则向量M1M2的方向余弦cosα,cosβ,cosy分别为 ()-|||-A. -dfrac (1)(2) ,-dfrac (sqrt {2)}(2) dfrac (1)(2) B. -1, -sqrt (2), 1-|||-C.1, sqrt (2) -1 D. dfrac (1)(2), dfrac (sqrt {2)}(2) ,-dfrac (1)(2)