The answer is C. The program prints:
quack

Why?
A dictionary stores pairs: a key and its value. sounds["duck"] looks up the key ‘duck’ and gives back its value.
Trace table
A trace table follows the program step by step. Here’s this one:
| key | value |
|---|---|
| mouse | squeak |
| dog | woof |
| duck | quack |
| cat | meow |
The code again
sounds = {
"mouse": "squeak",
"dog": "woof",
"duck": "quack",
"cat": "meow",
}
print(sounds["duck"])
Try it: change one number in the program and predict the new output before you run it.