the trees and plants can help ___ the air fresher and cleaner. A:making B:to make C:made选哪个?help后面不是跟原型吗?求解释

问题描述:

the trees and plants can help ___ the air fresher and cleaner. A:making B:to make C:made
选哪个?help后面不是跟原型吗?求解释

亲 help后面也可以加 不定式