简述AIDS的临床分期及各期的特点。
参考答案:
The World Health Organization warned that Asian countries _______ attentive to bird flu since
Asia _____ got rid of the disease completely. [ ]
A. should keep; has
B. must remain; has not
C. ought to stay; has been
D. shall be; has not been
学生在掌握长方形面积公式、三角形面积公式和面积相加性原理推导出梯形面积公式,加涅的学习分类标准属于( )
A.辨别学习
B.概念学习
C.规则学习
D.高级规则学习