有读者问这样一道选择题：
_____ day, Bill was starting his motorbike when his sister Mary came out and asked for a lift.
A. Some B. The other
C. Another D. On one
答案是B，为什么？
the other day指不久前的一天，故合句意。some day指将来有一天，another day指又一天，one day（其前一般不用on）指很久以前的某一天，都不合句意。
