建设项目环境保护措施应满足环境功能保护的客观需求，开发建设项目对下列哪几种生态环境不可采取生态恢复或补偿的方法( )

A．农田

B．湿地

C．草地

D．红树林

E．地质遗址

— How long do you think it is _____ he took up the job? 

— Half a year at least. [ ]

A. when

B. before

C. that

D. since