You can choose from all objects-even those you don't have permission to view. This lets you build report types for a variety of users. Once you save a report type, you can't change the primary object. If the primary object on a report type is a custom object, and the custom object is deleted, then the report type and any reports created from it are automatically deleted. If you remove an object from a report type, all references to that object and its associated objects are automatically removed from reports and dashboards based on that type. http://help.salesforce.com/apex/htviewhelpdoc?id=reports_defining_report_types.htm&language=en_us

Explanation
The solution that the app builder should configure to meet these requirements is creating three lead record types each with its own page layout containing the relevant fields. This way, the app builder can customize the fields and sections that appear on each record type based on the source of the lead. Option B is incorrect because creating a partner community and a record type for web and trade show leads does not address the requirement of collecting information that is unique to each type of lead, as partner community users may have different fields and layouts than internal users. Option C is incorrect because creating three sections on the lead layout and instructing users to collapse the non-relevant fields does not address the requirement of collecting information that is unique to each type of lead, as users may still see or enter data in the wrong fields. Option D is incorrect because creating custom page layouts for each type of lead only containing the relevant fields does not address the requirement of collecting information that is applicable to all sources, as users may miss some common fields.

To start tracking how many shoe subscriptions have been sold for each shoe catalog, a roll-up summary field should be created. A roll-up summary field calculates values from related records on a master-detail relationship. It can count, sum, min, or max numeric values from child records on a parent record.