The answer is D. The program prints:
CCC OOO DDD EEE

Why?
A for loop can go through a string one letter at a time. Each letter is printed 3 times in a row.
Trace table
A trace table follows the program step by step. Here’s this one:
| letter | printed |
|---|---|
| C | CCC |
| O | OOO |
| D | DDD |
| E | EEE |
The code again
for letter in "CODE":
print(letter * 3)
Try it: change one number in the program and predict the new output before you run it.