10. When I _______ (walk) into the room, everyone ________ (work).

When I walked into the room, everyone was working.

Explanation:

• "walked" is the Past Simple form of "walk", which is used because the action of entering the room happened at a specific point in the past.
• "was working" is the Past Continuous form of "work", indicating that the action of working was in progress when the first action (walking into the room) occurred.