The answer is D. The program prints:
BOA

Why?
word[3:6] is a slice: it starts at position 3 and stops before position 6. Positions count from 0.
Trace table
A trace table follows the program step by step. Here’s this one:
| position | letter |
|---|---|
| 0 | K |
| 1 | E |
| 2 | Y |
| 3 | B |
| 4 | O |
| 5 | A |
| 6 | R |
| 7 | D |
The code again
word = "KEYBOARD"
print(word[3:6])
Try it: change one number in the program and predict the new output before you run it.