truly和really在用法上有相似之处，也有不同之处，我们在前面一个地方已经回答过，仅就你的这个单句来看，用truly和really都可以。当然最通常的选择肯定是really。

查Longman Dictionary of Contemporary English（朗文当代英语词典）的truly词条，其第1条解释就是：

truly [+ adjective/adverb]

1. used to emphasize that the way you are describing something is really true

= really

His work is truly original.

Fawcett was a truly remarkable man.

该词典明确指出，用于此义时，truly=really。很显然它所给例句Fawcett was a truly remarkable man中的truly完全可以用really代替。