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单选题请回答20________

参考答案:H进入在线模考
Woman: It can get extremely noisy down here.The staff are supposed to wear ear protectors at all time but that's impossible if you need to talk to someone. The other things we have to contend with is dirt and dust. It's OK. When we're not too busy, by when there's a rush on, there isn't time to clear up.