改为同义句Mr.Smith was too excited to say a word

Mr.Smith was so excited that he couldn't say a word.

Mr.Smith was so excited that he couldn't say a word. Smith先生是这么激动，甚至说不出一句话来。

原句是too.....to 的结构，太....以至于不能....的意思。
so ...that 是如此.....以至于....的意思。

Mr.Smith was so exited that he couldn't say a word.

因为too…to 句型是说“太…以至于不能…”
而so…that句型是说“如此…以至于…”

因此在改变成so that 句型时，根据句意，要加一个not 。

希望可以帮到你

Mr.Smith was so exited that he couldn't say a word.

Mr.Smith was so excited that he couldn't say any word.

Mr. Smith was so excited that he can not say a word.