以学生为中心的教学策略不包括( )。
A．发现教学
B．情境教学
C．合作学习
D．程序教学
参考答案：D
This ________ my grandfather and those are my ________.
A．is; friends
B．is; friend
C．are; friends
D．am; friend
The number of people in the world ________ about 6 billion and large quantities of waste ________ each year.[ ]
A. totals; has been produced
B. totals; is produced
C. totals; are produced
D. total; are being produced
