Don"t cross the street when the traffic lights is red. lt"s really quiet _(danger）Mary always goes to school by bike.lt"s _(usual)for her to come here on foot.
问题描述：
Don"t cross the street when the traffic lights is red. lt"s really quiet _(danger）
Mary always goes to school by bike.lt"s _(usual)for her to come here on foot.
答