Final answer:
Diphtheria and pertussis are caused by bacteria larger than 5 microns; rubella and mumps are caused by smaller viruses.
Step-by-step explanation:
Among the diseases listed, diphtheria and pertussis (whooping cough) are caused by organisms that are greater than 5 microns in size. Diphtheria is caused by Corynebacterium diphtheriae, which is a gram-positive rod and can be found as part of the normal nasopharyngeal microbiota, but becomes pathogenic particularly when it produces the diphtheria toxin. Pertussis is caused by Bordetella pertussis and leads to prolonged severe coughing episodes. Both these bacteria are larger than the viruses that cause rubella and mumps, which are typically smaller than 5 microns.