To determine the most common car color, we can tally the occurrences of each color from Martin's recorded data:
- R (Red): 3
- G (Gray): 3
- W (White): 5
- B (Black): 7
Now, let's summarize the counts:
- Red (R): 3
- Gray (G): 3
- White (W): 5
- Black (B): 7
From the tallies, we can see that the color with the highest count is Black (B) with 7 occurrences.
Therefore, the answer is:
D. black