What causes meteor showers? a comet passing through Earth's atmosphere
a storm of asteroids suddenly leaving the asteroid belt
a change in the weather caused by a comet passing the Sun Earth's atmosphere passing through debris left by a comet's tail

The answer is going to be option C

if the type of the food available changes, then the frequency of beak types will change, because birds with beaks more suited to the available food will be more successful over time.

this is a good question! i'll do some research and come back when i have the answer!