题目内容：

Hummingbirds are birds from the Americas.They are among the smallest  birds.They get their name from the humming sound they make as they fly.

Hummingbirds live mostly on nectar(花蜜)，a kind of sugar water found deep inside flowers.Drinking nectar almost all day long gives hummingbirds the energy they need to keep their wings beating fast，typically around 3，000 times a minute.Hummingbirds' hearts beat fast，up to 1，260 times a minute(yours beats about 70)．And they breathe about 250 times a minute.So they need a lot of energy.This means that hummingbirds need to eat almost all day long.They fly from flower to flower，seldom at rest.

As a hummingbird feeds，its beak(鸟喙) and face get covered in pollen(花粉)．When the bird visits their flower，some pollen falls off.Hummingbirds help the flowers by spreading pollen around from plant to plant.It's a fair trade：the hummingbird gets a meal and the plant gets to make seeds(种子)．

For humans，eating sugar all day would lead to serious health problems.Our bodies could not deal with that much sugar.But hummingbirds burn their sugar as quickly as they eat it，so it doesn't become a problem.In fact，hummingbirds don't live on nectar alone.They also eat a lot of insects and spiders.And maybe with enough nectar，the spiders don't taste quite so bad.

1.How fast can a hummingbird's heart beat？(不超过10个词)

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2.How do hummingbirds help the plants to make seeds？(不超过10个词)

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3.Why is eating sugar all day not a problem for hummingbirds？(不超过15个词)

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