题目：The school rules state that no child shall be allowed out of the school during the day, ______ accompanied by an adult.
A. once
B. when
C. if
D. unless
喵查答案：D
本题考查省略的状语从句的连接词。句意应为“学校规章规定：除非有成年人陪同，否则孩子们在校期间不能出学校。”表示“除非”用unless。该句式构成了“连词+过去分词”结构。
