2．The underlined word "carnivores" ( in Para.2 ) refers to ________.

A．grass-eating animals B．meat-eating animals

C．polar bears D．Arctic seals

解析：词义猜测题。由画线词后面一句"The failure to save polar bears might result in loss of these predators."可知carnivores指"食肉动物"。

答案：B

3．If bears can't adapt to changing climates，we will probably have lost ________ by the middle of the 21st century.

A．most of polar bears B．few of polar bears

C．all of polar bears D．half of polar bears

解析：细节理解题。根据第五段第四句"It is estimated that if the bears cannot adapt to changing climates，they might die out before the end of the 21st century，with about 50% of the animals disappearing by 2050."可知，预计到21世纪中期约有一半的北极熊会消失。

答案：D

4．We can infer that ________.

A．using solar energy can help save polar bears

B．drilling for oil in the Arctic should be encouraged

C．polar bears can surely adapt to changing climates

D．nothing has been done to save polar bears so far

解析：推理判断题。根据最后一段第二句中的"These include finding new energy sources that don't give off greenhouse gases"可知，使用清洁能源有助于减缓全球变暖从而有利于北极熊的生存，太阳能不排放温室气体