Let a and b be valid Boolean expressions. Which of the following best describes the result of the expression a || b?

a) It will evaluate to true if a evaluates to true and b evaluates to true. It will evaluate to false otherwise.

b) It will evaluate to false if a evaluates to false and b evaluates to false. It will evaluate to true otherwise.

c) It will evaluate to true if a evaluates to false and b evaluates to false. It will evaluate to true otherwise.

d) It will evaluate to true if a evaluates to false or b evaluates to false. It will evaluate to true otherwise.

e) None of the above statements correctly describes the evaluation of the expression.