Write an expression that evaluates to true if and only if value of the boolean variable isamember is false.

!isAMember

Explanation:

isAMember is a boolean variable. It can have values true or false. We need to create an expression whose value is true if and only if isAMember is false.

For this we use the NOT or negation operator (!). If isAMember is false !isAMember will be true and conversely if isAMember is true !isAMember will be false. So !isAMember satisfies the required condition for evaluation to true.