If city noises are not kept from increasing,people will have to shout to be heart even at the dinner tabble 20 years from now.为什么是kept不是keep主句不是将来时态从句应用现在时啊
问题描述：
If city noises are not kept from increasing,people will have to shout to be heart even at the dinner tabble 20 years from now.
为什么是kept不是keep主句不是将来时态从句应用现在时啊
答
这是被动