You are asked to randomly choose 20 participants from 100 voluntary participants to fill a survey questionnaire that measures people’s attitude toward social distancing rules during the pandemic. Which of the following is a proper approach of randomization? ______
(1) Let the people who are not happy with the social distancing rules to fill the survey questionnaire
(2) Let young people to fill the survey questionnaire
(3) Let senior people to fill the survey questionnaire
(4) Use a computer to randomly select 20 participants from the 100 participants.
