You are judging photos for a pet contest. You have to rank 4 dog pictures from a total of 30, and 5 cat pictures from a total of 16. The number of possible permutations equals _____.
A. 30P4 + 16P5
B. 4! • 5!
C. 30P4 • 16P5
D. 30!/4! x 16!/5!