Theory of computation

Question

For any language $A$, $B$ and $C$ such that $A\subseteq B \subseteq C$, if both $A$ and $C$ are decidable, then $B$ is decidable.

True or False?

How can I find this?

Answer 1

Here is a counterexample: take $A$ to be the empty language, $C$ to be the full language (with respect to the given alphabet), and $B$ to be any undecidable language.