The cat knew to come just by the sound of what being opened?\nOptions:\n- tuna fish\n- food now\n- nap\n- train\n- four legs
A step-by-step solution is:
tuna fish
Cats like tuna fish.

Tuna fish comes in a can.

Can needs to be opened.

Tuna fish makes sound when opened.

.

So, the final answer is tuna fish