Question

Sperm cells must swim to the egg. What type of organelle must they contain? Why?

Answer 1

X and y chromosomes think of it like a phone charger you cant charge the phone unless the charger is plugged into the wall and the phone. 

Answer 2

I may be wrong, but they included 'swim' in the question. This leads me to believe they want you to say the tail. If sperm didnt have tails, they wouldnt be able to propel themselves towards the egg.

Hope this helps ~