You didn't tell what´s the temperature of the environment of the reaction. If you increase the temperature by 10 C when the enzime already reached the optimal rate, the enzime will be denatured. The correct answer would be increase the amount of substrate.
Increasing the temperature will make the molecules move faster, thus increasing the amount of collisions between substrate and enzyme. all the other three decrease rate: reducing the amount of substrate or enzyme reduces chances of collison, while changing the pH more than 1 number will most likely cause the enzyme to denature.