Final answer:
The marketer should modify the Smart List to limit the web page activity report to show only leads in Germany, as this section allows for setting specific criteria for filtering leads.
Step-by-step explanation:
If a marketer wanted to limit his/her web page activity report to only show leads in Germany, the section that should be modified is the Smart List. The Smart List is where you can set specific criteria to filter your leads based on certain attributes or activities. In this case, to filter by a geographic location such as Germany, the marketer would set up the Smart List to include only those leads whose location data matches Germany.