Which of the following is true? A)If we know that a reaction is an elementary reaction, then we know its rate law.
B)The rate-determining step of a reaction is the rate of the fastest elementary step of its mechanism.
C)Since intermediate compounds can be formed, the chemical equations for the elementary reactions in a multistep mechanism do not always have to add to give the chemical equation of the overall process.
D)In a reaction mechanism, an intermediate is identical to an activated complex.
E)all of these statements are true.

If we know that a reaction is an elementary reaction, then we know its rate law.

Explanation:

An elementary reaction is a reaction that takes place in one reactive encounter. This means that the two species interact in a single step to give the products.

If two reactants interact in a single step to yield the products then we can easily deduce the rate law from the reaction equation.

For instance, For the reaction;

2A + B → C

The rate law is

rate = k[A]²[B].

If the reaction is an elementary reaction and the equation of the reaction is balanced, then we can deduce the rate law from the balanced reaction equation.

it is the most commonly accepted one