Question

My sister is determined. ________ she has made up her mind, nothing can change it.

A．Though

B．Once

C．Unless

D．Until

Answer 1

B

试题分析：“一旦”下定决心，什么也不能改变（她的决心）。once: as soon as, when, 引导时间状语。A项引导让步状语从句；C项引导条件状语从句；D项引导时间状语从句，但是要求主句动词为延续性动词或动词的否定形式。故B项正确。