Access 2000采用的数据模型是（）。
A.层次型
B.网状型
C.环状型
D.关系型
参考答案：D
Which of the following theories assumes the main source of business cycle is most likely due to changes in technology and extemal shocks（）
A. Keynesian cycle theory.
B. Real business cycle theory.
C. New classical cycle theory.
黄绵土
