My hobby is collecting stamps.为什么要用ing的形式啊?

My hobby is collecting stamps.为什么要用ing的形式啊? Collecting stamps is my hobby 此句为何要用Collecting 为什么是is my My hobby is Collecting Stamps 的作文 My hobby is collecting stamps. Collecting stamps is my hobby. My hobby is collecting stamps My sister's hobby is collecting stamps.为什么sister后面要加's,为什么co my hobby is to collect stamps与my hobby is collecting stamps有 my hobby is 【collecting stamps】 对括号部分提问 My hobby is collecting stamps.在这里,callecting是什么成分 英语,以”My hobby is collecting stamps”为题写一篇不少于90词的短文. My hobby is collecting stamps 这句话的句子成分怎么划分,