英语的词性转换和改写句子,求理由

People in Switzerland enjoy skiing and【skating】in winter(skate)
答案解析：喜欢做某事：enjoy doing sth (动名词做并列宾语）
It takes Tom 'an hour and a half' to do his homework(对引号部分提问）
【How】【long】does it take Tom to do his homework?
答案解析：对时间长度提问,用how long
There is 'a' letter on the desk.（对引号提问）
【How】【many】【letters】_are there on the desk?
答案解析：多数量提问,用特殊疑问词：+可数名词复数how many +名词复数
I sometimes go to school on foot.（句意不变)
I sometimes【walk】【to】school.
答案解析:go to some place on foot =walk to some place
His ambition is to be an architect(句意不变)
He 【wants】【to】be an architect
答案解析：他的抱负是想成为建筑师,也就他成为建筑师；也就想做某事情=want to do sth；希望做某事情：hope to do sth

1 skating enjoy后面加动词ing形式
2 How long 对时间提问
3 How many letter 回答是a 一个 对数量提问
4 walk to on foot的意思是走路
5 want to/hope to ambition的意思是志向 这个答案很多 应该和你新学的单词有关