Final answer:
To improve an ad's relevance and increase ad rank for a given set of keywords, highlighting product uniqueness is the most effective action. This aligns the ad message with the search intent of the keywords, improving relevance and potentially increasing ad rank and exposure.
Step-by-step explanation:
To improve the relevance of an ad with a particular set of keywords and increase ad rank, the best action to take would be highlighting product uniqueness. This approach aligns the ad's message more closely with the search intent of the targeted keywords. By doing this, the advertisement becomes more relevant to the user's search query, which can lead to a higher quality score and thus improve ad rank. This, in turn, can lead to more exposure for the ad.
Adding more negative keywords is useful to prevent an ad from showing for irrelevant searches, which indirectly helps to improve the overall efficiency of the ad spend. However, it does not directly improve ad relevance to the targeted set of keywords. Focusing on connecting to a wider audience does not necessarily improve relevance to the specified keywords but rather expands the reach of the ad, potentially to less relevant users. Improving the navigation of the landing page enhances user experience after the click, but it does not influence the relevance of the ad in relation to the targeted keywords.