The answer is B. The program prints:
53

Why?
The loop remembers the biggest number it has seen so far, and replaces it whenever it finds a bigger one. This is how computers find the maximum.
Trace table
A trace table follows the program step by step. Here’s this one:
| n | n > biggest? | biggest |
|---|---|---|
| 13 | yes | 13 |
| 53 | yes | 53 |
| 2 | no | 53 |
| 44 | no | 53 |
| 51 | no | 53 |
The code again
numbers = [13, 53, 2, 44, 51]
biggest = 0
for n in numbers:
if n > biggest:
biggest = n
print(biggest)
Try it: change one number in the program and predict the new output before you run it.