Answer: Python Puzzler #1086

The answer is A. The program prints:

[43, 34, 21, 18, 10, 1]

Checked by running the program for real.

sort() puts the list in order, smallest first. reverse=True flips it, so the biggest comes first. It changes the list itself.

scores = [10, 1, 34, 18, 43, 21]
scores.sort(reverse=True)
print(scores)

Try it: change one number in the program and predict the new output before you run it.