亚马孙河流域的热带雨林遭受破坏对全球造成的严重后果是[ ]
A．水土流失加剧
B．生态环境受到威胁
C．野生动物遭劫
D．沙漠不断扩展
答案：B
. With their son ______ a foreign college now, the parents have some financial problems now and then.
A．to attend
B．attending
C．attended
D．having attended
Mrs.Smith is very _____. She has to sit down and rest every five minutes when she works.[ ]
A. well
B. healthy
C. unhealthy
D. good
