Answer
a) False
b) True
c) True
d) True
Work Step by Step
An implication p → q is true whenever the conclusion, q, is true, and whenever the premise, p, is false (in this case, the hypothesis being false, there is 'nothing to be verified' and the implication is automatically true). In other words, it is false only when the premise p is true, but the conclusion q is false.
In a) the premise $1+1 = 2$ is true, but the conclusion $2 + 2 = 5$ is false, so it is false.
In b), c) and d) the premise is false, so they are automatically true.
