ANSWER
C.

Step-by-step explanation
If Lamar uses 39 baseballs in 15 minutes, then he will use 4×39=156 balls in 60 minutes.
This implies that, Lamar uses 156 baseballs in an hour.
The total number of balls in the bucket is 260.
In an hour, the fraction of the baseballs in the bucket will be:

The correct choice is C.