1. What is the author's purpose in writing the story? 
A) He wants to tell the story of an extraordinary frog.
B) He wants to tell readers the characteristics of frogs.
C) He wants to show that frogs and humans can live together.
D) He wants to encourage readers to fight against pollution.

2. Finally the author realized that the frog preferred staying in the studio rather than in the greenhouse because ______. 
A) he wanted to remind the author that it's time to take actions against pollution
B) he enjoyed being there surveying the world through a computer with the author
C) he loved the tone of the computer which sounded like other frogs
D) he was afraid the pollution outside might affect his skin

3. Frogs are called an "indicator species" because ______. 
A) their lungs are turned inside out
B) their skin is dried up like paper
C) their skin is sensitive to environmental pollution and global climate change
D) frogs can warn people of environmental pollution by killing themselves

4. What does "sober folks"(line 7 from the bottom) refer to? 
A) People who are aware of the environmental problem.
B) Adults not addicted to alcohol.
C) People who lead a simple life.
D) Adults on the planet.

5. By saying "there are no boundaries" (line 3 from the bottom), the author indicates that ______. 
A) human beings have no more choices but act now
B) human beings and frogs are connected in the ecosystem
C) frogs can communicate with human beings in a certain way
D) the fight against pollution is endless