The science Festival is an occasion model planes and model rockets are flown over the sc

问题补充：

The science Festival is an occasion model planes and model rockets are flown over the school grounds.

A. that

B. when

C. where

D. which

答案：

A. that

(答案→)B. when

C. where

D. which

解析：考查定语从句：句意：科学节是模型飞机和模型火箭飞越校园的机会。先行词是occasion，机会，场合，表示“时间”，定语从句中不缺主语，宾语和表语，缺少的是时间状语，用when引导定语从句，选B。