The rules for determing the reaction order with respect to inividual reactants are as follows.

If the concentration of a reactant is doubled and the rate of product formation is doubled then the reaction is first order with respect to this individual reactant.

If the concentration of a reactant is doubed and the rate of product formation is quadrupled then the reaction is second order with respect to this indivudal reactant

If the concentration of a reactant is tripled and the rate of product formation increases by nine times then the reaction is third order with respect to this indivudal reactant

The rules for determing the reaction order with respect to individual reactants are as follows.

If the concentration of a reactant is doubled and the rate of product formation is doubled then the reaction is first order with respect to this individual reactant.

If the concentration of a reactant is doubled and the rate of product formation is quadrupled then the reaction is second order with respect to this indivudal reactant

If the concentration of a reactant is tripled and the rate of product formation increases by nine times then the reaction is third order with respect to this individual reactant

When the concentration of B doubles, the rate doubles. Making this reaction first order in regards to compound B. When the concentration of A doubles the rate is unaffected, making this reaction zero order in regards to compound A. This leaves a rate law of rate=k[B]

Zero-order reactions are independent of changes in the concentration of any of the reactants. The rate constant itself is dependent on temperature, so changing the temp will change the rate of a zero-order reaction.

An increase in temperature leads to an increase in reaction rate for endothermic reactions, while a decrease in temperature will slow down their rate.

For zero order reactions, reaction rate is independent of reactant concentrations; therefore, changing [A] and [B] will have no effect on reaction rate.

The rate law for this reaction would simply be , where k is the rate constant at a given temperature.

A zero-order reaction has a rate of formation of product that is independent of changes in concentrations of any of the reactants; however, since the rate constant itself is dependent on temperture, changing the temperature can alter the rate.

Intermediate is created and destroyed, and therefore does not appear on the net equation, which is . Thus, the intermediate is . Note that when asked for an intermediate, the coefficient in front of it is not used, rather we are looking for the species that is a product of one reaction and a reactant in a subsequent step.

The reactant  is not included in the rate law expression, and therefore altering its concentration does not affect the rate of the reaction. Catalysts always increase the rate of reactions by lowering its activation energy. Increasing temperature (average kinetic energy of the molecules) increases the frequency of collisions, and increases the proportion of collisions that have enough energy to overcome the activation energy and undergo a chemical reaction. Increasing the concentration of  will increase the rate of the reaction as indicated by the rate law.

For this question, we're asked to identify something that will always increase the rate of a reaction. Notice that the question specifically states "always."

Let's go through each answer choice and see how it affects the reaction rate.

When the concentration of reactants is increased, this may increase the reaction rate, but not always. For example, if a reaction is zero-order with respect to its reactants, then changing the reactant concentration will have no effect on the rate.

Just like with reactants, decreasing the concentration of products may or may not change the reaction rate. If the reaction rate is zero-order with respect to the products, then a change in their concentration will have no effect on the reaction rate.

A change in temperature is the only thing that is guaranteed to change the reaction rate. This is because changing the temperature will directly change the rate constant of the reaction. Increasing the temperature will increase the rate constant, and hence the reaction rate.