Turn the rule into gates

The rule is: the light turns on if A is 1 and B is 0.

The AND gate seems like the obvious choice. It fires when both inputs are 1. So let's try feeding A and B straight in.

Our winning combination is A=1, B=0.
AND sees 1 AND 0 and outputs 0.
The light stays off. Wrong answer.

What about OR? It fires when either input is 1.
With A=1, B=0 it outputs 1. Correct.
But with A=0, B=1 it also outputs 1, even though B is the bigger one. Also wrong.

We're stuck. AND only fires when both inputs are 1. OR fires when either input is 1. But what we need is a gate that fires when A is 1 and B is 0. None of these gates can do that.