ExCh1 Ambiguity 1b-a
Example: Pat didn't know a guest at the party.
Sorry, your answer is not correct. It is not the word know that is responsible for the ambiguity in this case.
Check again which type of ambiguity we have in this sentence. This may help you to answer this question, too. You can also consult the page with the explanations.
Of course, the word know is highly ambiguous: To mention just one example, there are cases of structural ambiguity which are caused by different complementation possibilities of the word know. One example would be I know what Alex wrote to Chris. Here the verb know either combines with an embedded interrogative clause or with a free relative, i.e., know either combines with a CP or an NP. This can be disambiguated by adding else (for the embedded interrogative reading) or ever (for the free relative).