Why Do Hummingbirds Emigrate from This Population of Scarlet Gilia

Multiple Choice

Why do hummingbirds emigrate from this population of scarlet gilia?

A) The flowers probably change their nectar production.
B) The flowers change from red to white,and the hummingbirds can't see them.
C) It gets darker on the mountainside,and the hummingbirds migrate to lower elevations where it stays light longer.
D) There is not enough information presented to answer this question.