从一个装有大小一样的2个白球和1个红球的盒子里，同时取出两个球，估计都是白球的机会是（ ）．
—________ the players ________ practice playing ping-pong every day?
—Yes. They want to join the World Table Tennis Championship (锦标赛). [ ]
A. Are; have to
B. Do; have to
C. Can; have to
D. Have; to
厌氧菌内源性感染分离率最高的是（）
A.厌氧消化链球菌
B.脆弱拟杆菌
C.产黑色素普雷沃菌
D.不解糖紫单胞菌
E.坏死梭杆菌
