They would put it beside their bed at night,on the seat when

They would put it beside their bed at night,on the seat when they s__ in a car or on a bus,and
In a school some trouble was caused by the students.They are very naughty and didn't obey the school rules.They often fought with each other and they didn't forgive each other.One day a new teacher came to this school.When he heard that,he came up with a good idea.
He told each of his students to bring a clear plastic bag and a bag of potatoes to school.For every person they didn't want to forgive in their lives,they chose a potato,wrote the person's name on it,and put it in the plastic bag.
Some of their bags were very heavy.They were then told to carry this bag with them everywhere for one week.They would put it beside their bed at night,on the seat when they s_____ in a car or on a bus,and next to their desk at school.Days of carrying the bags around with them made students get to know what a weight they were carrying in their minds.* And they had to pay attention to it all the time so they didn't forget it or leave it in embarrassing (令人难堪的) places.As time passed by,the potatoes went bad and smelt nasty.
Too often we think of tolerance as a gift to other people,and it clearly is for ourselves!* If we choose to keep our sadness and hatred (仇恨) in our hearts,we will have to carry them around all our lives.After that,the students got on well with each other and didn't fight anymore.Learn to forgive (原谅),and you will be happier at the same time.
用 sit 还是 sat
为什么

sat
您没有必要给我这么长的上下文
一句就够了
这是以前的
前面有when
所以是以前发生的
用sat
有什么不明白可以继续问,随时在线等.
再问： 答案是sit 2013年南京市建邺区中考第一次模拟考试 的题
再答： 不过看了好多知道回答都是sitting 但如果只有一个词语 只能用sat