The correct statements among the following regarding a complex reaction are-

a. Order of the overall reaction is the same as the molecularity of the slowest step.
b. Order of the overall reaction is less than the molecularity of the slowest step.
c. Order of the overall reaction is greater than the molecularity of the slowest step.
d. The molecularity of the slowest step is never zero or non-integer.
 

1. (a, b)
2. (b, c)
3. (c, d)
4. (a, d)

Hint: The molecularity of the slowest step is never zero or non-integer.
(a) For a complex reaction, order of overall reaction = molecularity of slowest step As the rate of the overall reaction depends upon the total number of molecules involved in the slowest step of the reaction. Hence, the molecularity of the slowest step is equal to the order of overall reaction

(d) Since, the completion of any chemical reaction is not possible in the absence of reactants. Hence, the slowest step of any chemical reaction must contain at least one reactant. Thus, the molecularity of the slowest step is never zero or non-integer.

Hence, option 4th is the correct answer.