新编四级听力练习 第274期

Section B
Passage One
26.
A. Diet.
B. Sleep.
C. Space.
D. Stress.
27.
A. They tend to reproduce more.
B. They may show more signs of violence.
C. They can eat and sleep better.
D. They may commit suicide.
28.
A. Rats can populate rapidly.
B. Population explosion can lead to violence.
C. Overcrowdedness may have the same effects on man.
D. It is a natural law that animals live and die.