To animals that live underground, what sense is the most important

I wasn't sure if it was sound, taste, touch, or smell.

There isn't much to hear underground and taste is more of a bonus for most animals; you don't need to taste that delicious dinner you're about to eat, but you'd like to, wouldn't you? Smell is hindered because underground just the coldness and the dampness messes with that sense. All that's left is touch-- and it's extremely important. Birds even rely on the importance that it holds to the worm to get their food by tapping on the ground, because the worm will travel towards it. Being able to feel can also assure you (since most underground creatures are blind or just have terrible vision) that you are not walking into a wall, or trying to penetrate something impenetrable. It can also alert to pain, and which actions or creatures cause that pain so that the animal or insect knows what to avoid to maximize survival chances.

Since taste is usually not as important, and most animals wouldn't " taste their way through" of a underground cave, I think rather smell, feel or sound can help. Feeling is probably the most important, so they can feel where the exit is, but smell is rather not useful , as you cannot smell anything but dirt.