"What exercise do you like the most?"

Translation: 你最喜欢做什么运动？

[Phillbo]

How about "你最喜欢什么运动？" Is the 做 necessary, could someone explain please?

[guayolove]

Really is not necessary. 做 運動 comes from do exercise. However other alternatives like 什麼樣的運動。 什麼運動是你最喜歡的 should be accepted. The way is programmed it is not quite accurate.