at; Children can go to school at the age of seven.
with; He went to work with his bike.这里一定不能用by
on；
at; Children can go to school at the age of seven.
on; He went to work on his bike.
on； the building on which a red flag
is flying
内容全部来源于网络收集，如有侵权，请联系网站删除：QQ：24596024