选矿对铁矿石有什么要求？
参考答案：
要求矿石品位稳定，波动小，按品种实行分采、分运、质量符合企业标准。
Tom hasn’t phoned us for a long time. What do you suppose _____ to him? [ ]
A. was happening
B. to happen
C. has happened
D. happened
带电测试绝缘子零值，当被测绝缘子串中零值绝缘子超过被测绝缘子总数7%时，应当更换全部绝缘子。
