article: 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 sitting 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   places. As time passed by, the potatoes went bad and smelt nasty.
  Too often we think of _ as a gift to other people, and it clearly is for ourselves! If we choose to keep our sadness and hatred   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 , and you will be happier at the same time.
question: From this passage we can know that   _  .
options: we should learn to forgive we should know something about potatoes we shouldn't use plastic bags we should take potatoes to school