GIVING IUT BRAINLEST NEED ANSWRR ASAP

What is an example of historical causation?
A. Rainbows are caused by sunlight in specific atmospheric
conditions.
B. European explorers arriving in the Americas brought new diseases
with them, which spread to indigenous people and caused many
deaths.
C. The changing weather between seasons causes many bird
species to migrate south for the winter and lay their eggs in
warmer climates.
D. People who left too early or too late on the Oregon Trail often died
because of harsh weather conditions, lack of food, and disease.