CNK CHALLENGE ON INFRENO ISLAND
This is kinda difficult.
Cimmediarely after start you will see a bridge, to the left of that bridge you will see a ledge with green grass and on the floor you will see a small hill of sand/water. When starting the race quickly go near the middle of the bridge and when its near its end. And quickly drive up the sand hill and push jump, if done correctly you will end up on the grass ledge with a Wumpa(Fruit) Box. When the path ends you will see the C.

N the N is not far from the C. Continue down the pathand you will see about 5 ? box's in a row quickly go to the right (the last two) and you should see a fallen pillar or what can now be used as a small ramp. the ramp has two differnt ends one big and one small. Gently go over the small one and slightly turn left. If you do this correctly you will get the N.

K the K is near the end. The K is located after the boxes and is located beyond the big hill with the turbo boost ramp (green and black ramp) Go on the hill and near its end you will see the K floating beyond it in the air. Now quickly jump(when at ramps end0 and you should get the K.

*NOTE THAT OBTAINING THESE LETTERS MAY TAKE MORE THAN ONE TRY, AND ARE PROBABLY BEST IF DONE IN THE FIRST OR SECOND LAP.