Answer:
At the next school assembly, ask every third student who enters whether or not they watch sports on TV
Explanation:
Students at a football game may like watching sports more than students who don't go to football games.
If Jillian wants to know about the students at her school, she should sample in a way that gives every student at her school an equal chance of being in the sample.
The answer for a more representative sample:
At the next school assembly, ask every third student who enters whether or not they watch sports on TV.