Which one of the following is CORRECT according to the news item?

In recent years there has been a string of high-profile celebrity suicides in South Korea. Authorities say many have been the result of hateful messages posted on-line. (21)Cyber-bullying, as it is called, is a big concern in South Korea, one of the world’s most wired countries. Some students are trying to counter bullies by flooding online forums with positive comments.
    Students at the Hogook Middle School in Ilsan, just outside of Seoul, have a unique assignment. Their task is to go online to message boards and other forums and write positive, cheerful comments. (22)Teachers and other adults hope those comments will discourage others from leaving vicious and negative remarks.
    Student Kim Hee-joo, 15, says on her school’s homepage she writes thank you messages to friends, family and teachers. And also when she sees people making bad comments about celebrities, she leaves nice messages, because when people see positive comments they are more likely to stop saying bad things and change their attitudes.