Which of the following statement is true about order of a reaction?

It cannot be fraction. It is defined only for elementary reactions but not defined for complex reactions. It can be determined theoretically. It is an experimentally determined quantity.

It is an experimentally determined quantity.

Facts about order of a reaction; (i) It is an experimentally determined quantity. (ii) It may be zero, whole number, fraction or negative. (iii) It is defined both for elementary as well as complex reactions.