当so,often,only等表示程度、频率的副词放在句首时,句子一般要倒装.例如：
Only in this way can you come up with a solution to the problem.
只有这样,你才有可能想出解决这个问题的办法.
only 及所修饰的副词、介词短语或状语从句放在句首时,要用：
only+ 状语+ be /助动词/情态动词+主语及其他
Only when he told me the news did I know what had happened.
Only in this way can you make progress in your English.