数据管理技术经历了人工处理阶段、【 】和【 】、分布式数据库系统、面向对象数据库系统5个发展阶段。
参考答案：文字系统
—Are there any balls under the chair? —________.
A．Yes, there is
B．Yes, they are
C．Yes, there are
D．No, there are
