Small-business owner Marcos set up his Google Ads campaign by thinking of "obvious" keywords off of the top of his head. What's one way he might improve them?

Answer:See the suggestions on the Opportunities tab

Explanation: The improvement in the Google ad can be made by the taking a look at the Opportunities tab which will display the adequate opportunities.

The tab displays these opportunities on the basis of the campaign settings, account's history, performance, style, trends etc and thus will create the appropriate opportunities accordingly. Thus Marcos will have to see the suggestion displayed on Opportunities tab