问题
选择题
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
答案
答案：D
连词题once一旦； when当…时候； if如果； unless除非。“学校规定白天学生不准外出除非有成人陪伴。”答案为D。