Ken enjoys bird watching. Every summer, he sees many ruby-throated hummingbirds in his garden. However, during the winter, he never sees any ruby-throated hummingbirds. Which of the following is a testable hypothesis that Ken could make to explain the winter absence of the hummingbirds?
A.
Where do ruby-throated hummingbirds go in the winter?
B.
Do ruby-throated hummingbirds like cold weather?
C.
Ruby-throated hummingbirds do not like being cold.
D.
Ruby-throated hummingbirds hibernate during the winter.