题目内容：

    Over their lifetimes, city trees will likely absorb less CO2 from the air than forest trees. A new study finds that city trees grow faster and die younger than trees in forests. Studies have shown forests readily absorb CO2. But there haven’t been much data on whether city trees grow, die and absorb CO2 at the same rate that forest trees do. So Lucy Hutyra, an environmental scientist, and her colleagues at Boston University in Massachusetts decided to find it out.

To figure out how quickly trees were growing the researchers tracked their diameters (直径) of their trunks from 2005 to 2014. The team focused on red oaks and red maples growing on Boston streets. These grew four times faster than the same species did in a nearby forest. Faster -growing trees absorb more CO2. Over the nine years the researchers have tracked these trees and found city trees absorbed four times as much carbon from the air as the forest trees did. The city trees also, however, were twice as likely to die.

City trees grow faster because they have less competition with their neighbors for light. In a forest, trees tend to grow close together, shading their neighbors. So few may get as much light as they want.

“Street trees also benefit from higher levels of nitrogen (氮气) in rainwater. Nitrogen is an element that helps plants grow. It’s also an ingredient (成分) of the. gas-burning cars’ exhausts. Some street trees also may have better access to water than trees in the country. That’s because the underground water pipes can leak,” says Hutyra.

Shaun Watmough, an environmental scientist, says it’s important to keep in mind that people plant city trees along city streets not just to absorb carbon. The trees also help clean the air, provide shade and make a city more beautiful even if it’s only for decades, not centuries.

1.What does the new research find?

A.City trees have larger economic value than forest trees.

B.Forest trees grow in a faster speed than city trees.

C.Forest trees are equal to city trees in number.

D.City trees have a shorter life than forest trees.

2.How did researchers know the growth rate of trees?

A.They exposed trees to strong sunshine.

B.They kept a record of the width of trees’ bodies.

C.They produced large amounts of car gases to trees.

D.They made trees compete for light against each other.

3.What can we infer about forest trees from the text?

A.They absorb more CO2

B.They have stronger roots.

C.They have more competitors than city trees.

D.They live in a nitrogen-enriched environment.

4.What is Shaun Watmough’s attitude towards planting city trees?

A.Approving. B.Doubtful.

C.Uncertain. D.Pessimistic.