①专一性 ②高效性 ③催化特性 ④在温和条件下进行.
A:①②
B:②
C:②③
D:①②④
— It's a very popular game. I like it very much.
如图,某水上乐园有一个滑梯AB,高度AC为6米,倾斜角为60°,暑期将至,为改善滑梯AB的安全性能,把倾斜角由60°减至30°