The enzymes activity is mensured to indicate the rate of reaction catalysed by that protein, the action of the enzyme is to decrease the time required for a natural reaction to occur, for example the sucrase breaking down the sucrose, or a lactase for lactose. Therefore, the option with a example that is similar to enzymatic activity is A. reducing the force a ball needs to start rolling down a hill (the force for the start of the movement is comparable with the activation energy of a chemical reaction). The other options present situations opposite to what is expected from the action of a catalyst molecule.