题目内容：

Frigatebirds seagoing fliers with a 6-foot wingspan, can stay aloft(up in the air) for weeks at a time, a new study has found.

Since the frigatebird spends most of its life at sea, its habits outside of when it reproduces on land aren’t well-known-until researchers started tracking them around the Indian Ocean. What the researchers discovered is that the bird’s flying ability is unbelievable.

Ornithologist(鸟类学家) Henri Weimerskirch put satellite tage(标签) on a couple of dozen frigatebirds. When the data started to come in, he could hardly believe how high the birds flew.

"First, we found, 'Whoa, 1,500 meters. Excellent,' " says Weimerskirch, "And after 2,000, after 3,000, after 4,000 meters-OK, at this altitude they are in freezing conditions, especially surprising for a tropical bird."

"There is no other bird flying so high relative to the sea surface," he says. "It’s the only bird that is known to intentionally enter into a cloud," Weimerskirch says. And not just any cloud—a soft, white cumulus cloud(积云). Over the ocean, these clouds tend to form in places where warm air rises from the sea surface. The birds take a ride on the current of rising air, all the way up to the top of the cloud.

Frigatebirds have to find ways to stay aloft because they can’t land on the water. Since their feathers aren’t waterproof, the birds would drown in short order. They feed by harassing other birds in flight until they bring whatever fish they’ve swallowed back into their mouth and the frigatebird takes it.

So in between meals, frigatebirds fly higher... and higher.

In one case, for two months-continuously aloft.

One of the tagged birds flew 40 miles without a wing-flap. Several covered more than 300 miles a day on average, and flew continuously for weeks. They are blessed with an unusual body. No bird has a larger wing surface area compared with body weight.

1.How did researchers feel when data about frigatebirds reached them?

A. Calm.    B. Surprised.

C. Hopeful.    D. Anxious.

2.According to the text, how can frigatebirds fly so high?

A. By flying into a cloud.

B. With the help of researchers.

C. Thanks to advanced technology.

D. By following other birds into the sky.

3.What does the underlined word “they” in the text refer to?

A. Frigatebirds.    B. Other birds.

C. Small fish.    D. Larger fish.

4.In what aspect are frigatebirds different from other birds?

A. When they give birth.    B. What they feed on.

C. Their body weight.    D. Their wing surface area.