Causality and Conditionality

[YiX773]

A alone is enough to cause B.
Does that mean: A -> B? (A is there, and it's enough to cause B, so B is there too.)

A is a contributing factor of B.
Does that mean: B -> A? (For B to be there, you need A, which is a contributing factor.)

Please help!

[YiX773]

Oh! Causality! It's bi-conditional !!