Adrienne has a pet mollusk. Lately she noticed that her pet has learned how to escape its tank. What kind of mollusk is Adrienne's pet? What makes you believe this?

The highest probability is that Adrienne has a pet octopus.

The reason why I think that Adrienne's pet mollusk is an octopus is from multiple reasons:

- The octopuses are mollusks

- They have tentacles, eight of them, all able to catch things and perform certain things with them

- They are one of the most intelligent animals, and they are also animals that manage to learn from observing. The octopuses actually have nine brains, one central, and one in each tentacle, and all of them can act individually

- The octopuses are extremely elastic, can twist, change shape, and are considered as the masters of escaping as they can get out from pretty much everywhere if it is possible