题目

—When __ your mother __ you that blue dress, Mary? —Sorry, I really can't remember. A. does; buy         B. has; bought              C. had; bought             D. did; buy 答案：D永安天宝岩自然保护区是 A．农田生态系统   B．森林生态系统            C．草原生态系统    D．城市生态系统