how long have you ___this book ? a. bought b.buy c had d buying

how long have you ___this book ? a. bought b.buy c had d buying
为什么

how long have you____? how long have you been 用法 How long have you been skating? How long have you been collecting shells？与How long have you collected shells?的区别 how long have you been here 和 how long have you stayed here 的区别 how long have you been keeping this to yourself? How long have you been married? 你们结婚多久了？ how long have Liji and Guoda been married? How long have you been like this?是什么意思？ How long have we been run?错在哪里