— Helen, would you like to go to the park with me?
— .
A:Sorry, I wouldn't
B:Yes, I'd love
C:That's right
D:That's a good idea
关于地震、滑坡这两种地质灾害成因的说法,正确的是( )
在生态系统中,生物的种类、各种生物的____和____总是维持在相对稳定的状态,这种现象就叫做生态平衡.