题目内容：
根据以下内容，回答题。What’s the best way to protect a tender, green seedling from the hungry stomach of deer? Give the seedling bad breath!
The same chemical that gives people bad breath after they have eaten garlic can save small trees from being eaten by animals.
A kind of chemical selenium(硒), which is also found in garlic, is planted in the soil near a young tree.The tree’s roots absorb the selenium which is then carried to the leaves.
From there the selenium is used to form a chemical called dimethyl selenide (乙烷硒化物)-the same chemical made in the human mouth after eating garlic．As deer wander around looking for food, they smell the seedlings’ leaves and leave the plants alone.
The selenium is important.Why? Because each year deer eat millions of dollars’ worth of trees farm seedlings.
So far, selenium has been tested only on Douglas fir (枞树) seedlings, but researchers think they could protect fruit trees and garden plants, too.
When people eat garlic, ________. A．they send out a horrible smell
B．they are out of breath
C．they will feel sick
D．it is hard for them to breathe
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