If A = 1 and B = 1 what is the output of the logic circuit below?
Forget the A input, if B=1 the X-labeled transistor becomes a pull-down, which forces a 0 at U and V. U then pulls-up, and your output becomes 1.

For illustration, consider the same schematic with the transistors replaced by switches. You can see that, when B=1, the A input doesn't come into play.