Which of the following can affect the activity of enzymes?

temperature, pH, enzyme concentration, substrate concentration, and the presence of any inhibitors or activators.

The factors affecting the enzyme activity are temperature, pH, and substrate complex.

Explanation:

The enzymes are proteins and increase the biological reaction.

Different factors affect the enzyme reaction - temperature, pH, and substrate concentration.

When an enzyme comes in contact with a substrate, it forms the enzyme-substrate complex. The temperature increases the kinetic energy of the enzyme and the formation of the enzyme-substrate complex will be more. But after a certain level, the increase temperature rate decreases the three-dimensional structure of the enzyme. As a result, the enzymatic activity decreases.  

The pH also has played a role in maintaining normal enzyme activity. The alteration of pH causes the disturbance of enzyme reaction. In the stomach due to pepsin, HCl, the environment is acidic. It kills the intestinal bacteria. But if this pH level decreases, it causes trouble to our gut.

Another factor is substrate concentration, which affects the formation of the enzyme-substrate complex. The substrates combine with the active site of the enzyme. If there is a number of the substrate the active site will be filled and increase the reaction rate. But after some time all the active sites are filled and it leads to a saturation of the enzymatic reaction.  

the answer is:

carbon dioxide