slb连接数暴涨:How long have you been collecting shells？与How long have you collected shells?的区别

how long have you been 用法 How long have you been ____Greener China ? A.with B.at C.from D.through How long have you been collecting shells？与How long have you collected shells?的区别 How long have you been collecting shells？与How long have you collected shells?的区别 How long have you _______(have) this book? How long have you __?Since 1990.A.bought MP3 B.joined the Party C.lived in the town HOW long have you been studying english 怎么回答 how long have you been in love with your boss? how long have you been in love with your boss? how long have you been keeping this to yourself?