Question

— Could we practice playing the guitar in the hall, Sir ?                  
—No , ___________ you have the principal’s (校长) note.        

A．if

B．unless

C．because

D．since

Answer 1

B

试题分析：句意：先生我们能在大厅练习弹钢琴吗？不行，除非你有校长的批条。A. if如果B. unless 除非，如果不C. because因为D. since自从……。根据句意，故选B。