Answer:
Washing Clothes & Dissolving Sugar
Explanation:
Think about each application:
1) Washing clothes: You kind of need water to do this, or not much washing can be done.
2) Linking brake pedals to the brake pads: You don't need any liquids for this. You need solids.
3) Deodorizing a room: You would problem choose an aerosol, which is sprayed, thus a gas.
4) Carving a sculpture: You would use solid tool and a sold sculpture.
5) Dissolving sugar: You need a liquid to dissolve sugar!
6) Painting a wall: Perhaps, you COULD say that the paint is a liquid... but I'm not sure if that really counts. I believe this application would still be solids.
7) A gear for a machine is a solid!