如图,△ABC中,∠ACB=90°,CD⊥AB于D,BD=2,AD=8,求S△ABC.
— So many problems! I'm too tired.— You should try to _____________ them by yourself. You're not a child any longer.
下列各项中划线的词语,使用恰当的一项是( )
①维持生态平衡 ②促进生态系统的物质循环 ③帮助植物传粉、传播种子