题目

（05年辽宁卷）两光滑平板MO、NO构成一具有固定夹角θ0=75°的V形槽，一球置于槽内，用θ表示NO板与水平面之间的夹角，如图5所示。若球对板NO压力的大小正好等于球所受重力的大小，则下列θ值中哪个是正确的？（    ）       A．15°                   B．30°                   C．45°                   D．60°To______, she keeps on exercising every day as well as________.A. lose weight; goes on a diet B. lose her weight; going on a dietC. lose weight; going on a diet D. lose her weight; go on a diet