For a multi-step reaction, the rate-determining step is the step with the highest activation energy. Be careful not to confuse this with the energy transition state.

A catalyst is used to increase the rate of a reaction. By definition, it does so without being consumed during the reaction. Thus the choices that talk about decreasing the rate of reaction are wrong. Catalysts decrease the activation energy of a reaction.

The concentration of the enzyme is independent of the rate constant because the enzyme can only catalyze the conversion of reactants to products at a specific rate. Increasing the concentration of the enzyme, however, would increase the absolute number of reactions occurring simultaneously; thus, the rate of reaction (but not the rate constant) would increase.

This question asks us how the rate of the reaction would change if temperature were increased. Increasing the temperature increases the relative velocity of each reactant, increasing the chance that two reactants collide and are able to form a product with the help of carbonic anhydrase. This can also be seen with the following equation.

Increasing the temperature decreases the denominator because e^E/RT becomes e⁰ = 1 as the temperature increases. The overall effect is an increasing in reaction rate.

Note however, that the temperature can only increase up to a point. Once the temperature becomes too high, the enzyme would denature and no longer work.

Extreme temperatures and pH levels decrease the activity of enzymes because they become denatured. In the body, most enzymes work optimally around a pH of 7.4. Increasing the pH too high would denature a protein because amino acids that are normally protonated at physiological pH (i.e. acidic residues) would become deprotonated. Lack of protonation would cause collapse of the tertiary and quaternary structures, leading to a decrease in enzyme function. 

Extreme temperatures and pH levels decrease the activity of enzymes because they become denatured. In the body, most enzymes work optimally around a pH of 7.4. Decreasing the pH too low would denature a protein because amino acids that are normally deprotonated at physiological pH (i.e. basic residues) would become protonated. Protonation would cause changes in tertiary and quaternary structures, leading to a decrease in enzyme function, thus the concentration of the product in the catalyzed reaction would decrease as well. 

Catalysts do not shift the equilibrium position of a reaction in favor of the products.

Catalysts speed up chemical reactions by lowering the activation energy (E_a) of reactions, but do not affect the equilibrium position since the change in rate from reactants to products speeds up proportionally to the change in rate from products to reactants (the same K_eq will be achieved whether a catalyst is used or not).

A catalyst affects activation energy; an inhibitory catalyst increases activation energy. Catalysts do not affect equilibrium concentrations of products or reactants.

A catalyst is a substance that increases the rate of a reaction without being altered or used up in the reaction. Both the forward and reverse rates of the reaction are accelerated by a catalyst. Slowing the reverse rate, with an increase in forward rate, would result in a shift in equilibrium. Remember that a catalyst will never change the equilibrium constant (K_eq) of a reaction.

Remember that catalysts affect the kinetics of a reaction, but will not affect the equilibrium. As a result,  will remain the same in the presence of a catalyst, though the reaction rate will accelerate.