crossing the river to school其中的cross为什么要加ing

crossing the river to school 这个题目crossing为什么是ing 啊在句中做什么成分 翻译Crossing the River to School全文 Be careful when crossing the road中的cross为什么加ing Mary is swimming ___ the river.A、to cross B、crossing C、cross Crossing the River to School(七年级下册英语） 有没有适合crossing the river to school这篇英语课文的音乐 七年级下册三单元2b crossing the river to school 里面的词组有哪些? 谁能帮我把Crossing the River to School全文改写成过去式? 适当形式填空说为啥要这样填1.they have to go(cross)the river to school eve Cross.The.River.的意思 these students go on a ropeway to cross the river to school go,a,school,to,the,these,on,to,ropeway,students,cross,river连