Outline: 1. 学生打工现象很普遍； 2. 为什么大学生要打工； 3. 学生打工应注意的问题。 Why Do College Students Take Part-time Jobs

A．An important new role has evolved for good zoos: they are not prisons for animals but reservoirs of species.
B．Zoos should learn to justify their existence no matter how great the pressure is.
C．Criticism on zoos ought to be more specific because zoos are not graded on the same level.
D．The function of education of zoos becomes more important and practical.

A．animal welfare grounds
B．collections
C．prisons
D．areas where zoos are built