only by doing so can we help to make the world a better plac

因为only在句首 所以句子要部分倒装 即本来是we can help 变为can we help 句意为：只有这样做,我们才能让世界更美好.
还有几种情况 要部分倒装 如 Not ...until在句首时 例：
Not until midnight did Tom came home.