What does mutual information signify between two random variables, X and Y , in the context of information theory?

Correct option is B

​$$\text{In information theory, mutual information } I(X;Y) \text{ measures how much knowing one random variable reduces the uncertainty about the other.} \\[8pt]\text{Mathematically:} \\[6pt]I(X;Y) = H(X) - H(X|Y) = H(Y) - H(Y|X) \\[8pt]\text{This represents the \textbf{shared information} between } X \text{ and } Y .$$​​