Task: Question Answering
Input (English): Question: Machines A and B produce bottles at their respective constant rates. Machine A produces k bottles in 2 hours and machine B produces k bottles in 4 hours. How many hours does it take machines A and B, working simultaneously, to produce 15k bottles?

 Option A: 10

 Option B: 15

 Option C: 12

 Option D: 20

 Option E: 18
Output (English): Option D