同时投掷三颗骰子，于少有一颗骰子掷出6点的概率是 (结果要求写成既约分数）.
考虑对立事件，.
—How long did you watch TV in the room?
—_____.[ ]
A. I felt a little tired
B. Twice a week
C. About two hours
D. It's wonderful
凡进入硫化氢环境的人员必须接受（）教育培训，经考试合格，并经上岗前（）合格后方可持证上岗。
.
.