问题
选择题
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
答案：B
题目分析：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。