The word "They" in paragraph 2 refers to ______.

A. predictable

B. unpredictable

C. changeable

D. unchangeable

A. reduced considerably

B. put a tick

C. examined carefully

D. motivated to develop

A. a kind of harmless animals

B. an achievement of human beings

C. a harmful factor to the environment

D. a kind of useful plants

A. expose foods to sun and wind

B. remove moisture from foods

C. produce pemmican

D. moisten foods

A. chamber

B. flat

C. area

D. studio

A. Environment pollution is real.

B. Reasons why low-lying areas are flooded.

C. Solutions to global warming.

D. Reasons why global warming is a problem.

A. higher temperature

B. coastal erosion

C. increasing sea level

D. stable rainfall