1. a number of，the number ofa number of 许多，谓语动词用复数；the number of 的数目，谓语动词用单数。The number of students is increasing.学生的数量在增长。2. in front of，in the front ofin front of 范围外的前面；in the front of 范围内的前面。In the front of the room sits a boy.在这个房间前面坐着一个男孩。3. three of us，the three of usthree of us 我们（不止三个）中的三个；the three of us 我们三个（就三个人）。The three of usTom, Jack and I went to the cinema yesterday.我们三个汤姆、杰克和我昨天去看电影了。4. by bus on the busby bus 乘公交车，表手段，方式，不用冠词；on the bus
