Which of the following is an example of when the query cache would avoid roundtrips...

Query Cache: The query cache in IBM Cognos Analytics helps to store the results of frequently executed queries to improve performance.

Avoiding Roundtrips: When the same master-detail request is executed repeatedly, the query cache can serve the results from the cache instead of making another roundtrip to the database.

Performance Improvement: This reduces the load on the database and speeds up the report generation process by utilizing the cached data.

Reference: IBM Cognos Analytics V11.1.x documentation details the functionality of the query cache, including its ability to handle repetitive master-detail requests efficiently by avoiding unnecessary database roundtrips.