with句型? there should be no more than four such excursions per day with at least 60 minutes between exposure limits and the daily tlv-twa limit must not be exceeded. 这句中每个词我都明白, 只是不明白红字在句中的作用, 所以我整句就没明白. tlv-twa是 threshold limit values- 时间加权平均浓度值. 谢谢 查看更多