Answer: list @mystage;

The correct command to list files in an internal stage is `LIST @mystage;`. According to Snowflake documentation and the community discussion consensus (with multiple comments receiving upvotes), internal stages are referenced using the `@` prefix followed by the stage name. Option A (`list @mytable;`) is incorrect because `@mytable` refers to a table stage, not the internal stage `mystage`. Option B (`list @%mytable;`) is incorrect as `@%mytable` specifically refers to the table stage for `mytable`. Option C (`list @%mystage;`) is invalid syntax as `@%` is used for table stages, not named internal stages. The community discussion clearly indicates that internal stages use the `@` prefix without additional symbols, making D the only correct choice.

Author: LeetQuiz Editorial Team