我国一些城市在绿化过程中。耗费巨资移植大树进城。据统计，移植大树的成活率不超过60％。据此回答问题。移植大树成活率低的最主要原因是（　 ）

A．病虫害防治不力

B．移植过程中受损伤

C．生存环境改变

D．人为破坏严重

Ms Marsh was such a careless group leader that she ______ a very important detail when laying down the plan for the project.

A．left behind

B．left aside

C．left out

D．left off