The answer is C. The program prints:
9 5 1 Lift off!
Why?
The loop keeps going while count > 0. Each time round it prints count, then takes away 4. When count reaches -3, the condition is false, the loop stops, and the last line prints.
Trace table
A trace table follows the program step by step. Here’s this one:
| count | count > 0? | new count |
|---|---|---|
| 9 | yes | 5 |
| 5 | yes | 1 |
| 1 | yes | -3 |
| -3 | no (stop) |
The code again
count = 9
while count > 0:
print(count)
count = count - 4
print("Lift off!")Try it: change one number in the program and predict the new output before you run it.