Peppered moths often hide on white-colored birch trees because they are similarly colored. Which of the following environmental changes would lead to the enhanced survival of darker moths?

A) Warm weather causes the birch trees to grow their leaves back early.

B) Birch trees become covered in black ash from nearby factories.

C) Heavy rainfall causes birch trees to grow taller than normal.

D) Disease kills off more than half of the birch tree population.