Based on the main idea, which would be the best title for this passage?
A.
Hummingbirds in Danger of Starvation
B.
Feasting on Flower Nectar
C.
The Highest Metabolism in the Land
D.
The Torpor of the Hummingbird

With the exception of insects, the hummingbird has a higher metabolism than any other animal. Metabolism is the process by which an organism breaks down its food and gains energy from it. The hummingbird must metabolize its food quickly in order to get enough energy to beat its wings. It needs a lot of energy, especially when you consider that some species of hummingbirds beat their wings as often as 100 times per second! In order to keep its wings beating, the hummingbird visits hundreds of flowers every day. Over the course of a single day, a hummingbird consumes its own weight in flower nectar.
With its ability to consume and break down a large quantity of nectar, it might seem as though the hummingbird's high metabolism would be the envy of the animal world. However, because of the hummingbird's fast heart rate and rapid wing beating, it must eat constantly in order to stay alive. In a sense, the hummingbird is continuously hours away from starvation.
Still, the hummingbird is a survivor and is able to store enough energy to rest from time to time. It does this by slowing down its metabolism and entering a state known as "torpor," which is similar to hibernation. During torpor, the hummingbird's heart rate and rate of breathing slow down. Its need for additional food and energy is reduced.