My hobby is collecting old coin.和My hobby is to collect old

My hobby is collecting old coin.和My hobby is to collect old my hobby is collecting coin.为什么不是collect coin呢? my hobby is collecting stamps 和 my hobby is to collect stamp my hobby is to collect stamps与my hobby is collecting stamps有 To collect kites is my hobby与Collecting kites is my hobby一样不 my hobby is to collect coins.my hobby is collecting coins 我见 改为同义句My hobby is collecting old coins My hobby is collecting stamps. Collecting stamps is my hobby. My hobby is collecting stamps 单选：My hobby is ( )mathbox covers.A.to collect B.collecting 应 My hobby is Collecting Stamps 的作文