1.B 因为出现了具体时间就要用on,即on a cold winter morning,in the morning
2.A hear sb doing sth.听到某人正在做某事,hear sb do sth.听见某人经常做某事,或强调全过程.这里没有sing这个选项所以也只能选singsing,
3,B a number of 许多,大量,与a lot of 意思接近,后面都可以加可数名词复数和不可数名词.而the number of 译为:.的数量,much后面只能加不可数名词,只能说many fresh apples 因为many后面只能加可数名词复数!
4,C 英语中能修饰比较级的词有:much ,far ,even ,a little,any 等等
5.Tom had a little accident yesterday.
6.What happened to him yesterday?
7.I happened to meet Mary on the street just now.