Which sentence best describes a hummingbird as a living system that is
made up of several less complex systems?
A. A hummingbird's wing can flap at speeds between 12 and 80
beats per second.
B. The hummingbird is one of the smallest bird species in North
America.
C. A hummingbird's body includes a skull and many small bones.
D. Hummingbirds eat flying insects and spiders.