White cannot play to A, because white stone would not have liberties. Also white cannot play to B, because again white stone would not have liberties. So white cannot start killing at all.
Making or preventing two eyes can get very difficult. When learning it is good to play out any unclear situations. Reading out all positions can be difficult.
It may look like black has two eyes. But in reality black has only one eye. White may need multiple moves to capture black stones, but eventually white can capture black.
