Only in this way can you solve this problem.Only then did he understand what the headteacher meant.Only after they had discussed the matter for some hours did they reach a decision.

• 二、要点归纳：位于句首修饰状语（副词、介词短语或状语从句）时，句子（如有主从句只能是主句）使用倒装语序（部分倒装）。