The answer is B. The program prints:
banana

Why?
A negative position counts from the end: -1 is the last item, -2 the one before it. So -3 means item number 3 from the end.
Trace table
A trace table follows the program step by step. Here’s this one:
| position | negative position | item |
|---|---|---|
| 0 | -5 | grape |
| 1 | -4 | mango |
| 2 | -3 | banana |
| 3 | -2 | apple |
| 4 | -1 | plum |
The code again
basket = ["grape", "mango", "banana", "apple", "plum"]
print(basket[-3])
Try it: change one number in the program and predict the new output before you run it.