阅读理解。

Polar bears live in the coldest environments on Earth-the Arctic. Called 'ice bears'in many
European languages, polar bears depend on the ice that surrounds them for their survival. As the
Arctic climate changes and the ice slowly disappears, polar bears face an increasingly uncertain
future.
Polar bears impress us with their incredible size, power and ability to survive in the cold Arctic.
These giants can stand three meters tall and weigh over 500kg, and they spend their lives traveling
throughout the Arctic. Two layers of fur keep them warm. Interestingly,the hairs are hollow in order
to direct the sunlight straight to the skin. Undemeath their fur, polar bears have an
additional l0-cm-layer of fat.
Polarbearshuntringed seals (环斑海豹), which live under the Arctic ice. They wait patiently
for hours beside holes in the ice pack (浮冰群) for seals to suce and breathe. Using their great
strength , the bears pull the heavy animals up onto the ice. The seals provide much of the fat the
bears need for warmth.
Since 2006 , polar bearshave beenlabeleda vulnerable(脆弱的) species. Most experts feel
the threat to polar bears comes not from hunters or predators(食肉动物),but from the gradual melting
of Arctic ice. Due to global climate change, the Arctic region is getting warmer. Arctic ice is breaking
up earlier in the spring, and its area is decreasing.
Problems polar bears around Canada's Hudson Bay are facing may indicate what lies ahead for
polar bears elsewhere. Hudson Bay is located at the southern limit of the polar bears' territory(领地) .
Currently,the ice there breaks up three weeks earlier in the spring than it did 20 years ago. Polar
bears on Hudson Bay fast during the summer,waiting for ice to form in the fall to hunt. Every year,the
Summer gets longer, and the bears get skinner. Over the past 25 years, the average weight of the
female bears has dropped 68kg. This loss affects their ability to reproduce, and already the number
of births has dropped 15% . Unless the bears can leam to survive global climate change, the giants
of the ice may one day disappear.

1. What puts polar bears in a challenging situation in the future?
A. More humans hunting in the Arctic.
B. The warming climate and melting ice.
C. The reducing number of food resources.
D. The changing weather and new habitats.
2. Paragraph 2 is mainly concemed with___________.
A. the description of polar bears
B. polar bears' pattern of survival
C. brief information on polar bears
D. the types of polar bears
3. Which description of polar bears is TRUE?
A. Polar bears are usually of medium size
B. Polar bears feed mainly on ringed seals.
C. In winter polar bears live under water.
D. Polar bears travel beyond the Arctic in summer.
4. The female bears have lost weight greatly in the past decades because___________.
A. there are a few ringed seals to hunt
B. winter days are getting much longer
C. they have to give birth to more young
D. they have to wait longer before hunting
5. We can feel that the author's tone for polar bears is__________.
A. sympathetic
B. optimistic
C. hopeful
D. indifferent