He injured his leg and ______ couldn’t play in the game.[ ]

A. therefore  

B. however  

C. in which case  

D. in this way

景观异质性是（）因素共同作用的结果

A．干扰

B．资源环境的空间分异

C．物质循环

D．生态流的空间聚集和扩散

E．生态演替