S3 (4.3) Popular sports

How do you spell the noun of 'popular'?

What's another word for 'take part in'? (Hint: part_)

How do you spell 表演 in English? (Hint: perf_)

How do you spell 比賽 in English? (Hint: comp_)

What's another word for a 'sports player'? (Hint: ath_)

To _ all athletes are playing a fair game, having a referee is a must in a competition.

• sure

• help

• give

• ensure