LSAT Practice Test

How would you express the relationship between two elements A and B when A cannot be selected unless B is selected in Formal Logic?

1. A → B, ~B → ~A

2. B → A, ~A → ~B

3. A → ~B, ~A → B

4. B → ~A, ~B → A

The correct answer is: A → B, ~B → ~A

In formal logic, the relationship between two elements A and B where A cannot be selected unless B is selected is represented by the conditional statement "A → B", which means "If A, then B". Additionally, the relationship can be further expressed as its contrapositive "~B → ~A", which means "If not B, then not A". This captures the essential relationship between the two elements in this scenario, making choice A the correct answer. Choices B, C, and D do not accurately represent the relationship where A cannot be selected unless B is selected and thus are not correct in this context.