我妈妈离开家的时候忘记关灯了.
I believe exercise and (新鲜的)air are good for our health.
It's important for teenagers to have good (习惯)
Jack looked through the (介绍)about the book before he decided to buy it.
Students should answer questions loudly and (清楚)in class.
Do you need to (讨论)the problem in groups?