They could both be correct. I there are pictures of tomatoes on the side of a truck, or if there are tomatoes on the bed of a truck, then #2 is correct. If the truck has tomatoes inside it, then #1 is correct.

Your first example.

Tomatoes are in the truck.

And instead of writing which one is "right", you should use which one is "correct".

Both can be correct. But in most of the time the correct one is tomatoes are in the truck...