On October 16, 2000 British Broadcasting Corporation (BBC) cited the result of the "Emotional Health Survey" conducted in the UK . Among the 400 respondents, 25% feared a hopeless future 33% felt downright miserable and nearly 10% thought that their death would make things better for other. What should we consider to determine whether the result of the survey can be generalized to the entire British population? Select all that apply

1. The sampling method used

2. Whether the survey randomly assigned respondents to the treatment or the control group

3. Whether the survey included a control group

4. The response rate

5. Whether the survey blocked on the age of respondents