How does your stomach tell your brain its hungry?

Idon’t know the answer and i’ve been stuck on it for a while now skskskskks

Fruit bats in central america eat bananas and other fruits. banana plants rely on bats for pollination. what would be the most likely consequence on the banana crop if fruit bats were eliminated from the area? the banana crop would increase because bats would stop eating the crops. the banana crop would decrease because bats would no longer pollinate the crops. the banana crop would remain constant because bees would replace the bats. the banana crop would remain constant because the plants would adapt using asexual reproduction.

Which of these is a provisioning service people get from the ocean