问题补充：
，John returned to school from his hometown.
A. The summer vacation being over
B. The summer vacation is over
C. Because the summer vacation over
D. After the summer vacation being over
答案：
(答案→)A. The summer vacation being over
B. The summer vacation is over
C. Because the summer vacation over
D. After the summer vacation being over
解析：
做题时首先分析句子结构，确定句子类型。此处应为独立主格结构作为主句的原因，对主句解释、说明，故A项正确。B项为完整的句子，两句间缺少连词；C项是because引导的原因状语从句，句中缺少谓语；D项是after引导的时间状语从句，谓语动词应为was。
