The correct answers are C and E. Executing a stored procedure (C) requires a running virtual warehouse because stored procedures execute SQL code that needs compute resources. Querying data from a materialized view (E) also requires a running virtual warehouse because, although materialized views store pre-computed results, the query execution still needs compute resources to access and return the data. Options A (downloading data from an internal stage) and B (listing files in a stage) do not require a warehouse as they are metadata operations. Option D (altering a table) is a DDL operation that does not require a running warehouse, as it only changes the table structure without processing data. The community discussion, with the top comment (79% upvoted) and multiple confirmations, supports CE as the correct choice, aligning with Snowflake documentation that highlights compute needs for stored procedures and materialized view queries.