The following are types of active surveillance except

a. National household surveys gathering information on the social status and health status of people in a particular country

b. Notifcation of diseases by health workers in health facilities is required by law.

c. Observing groups of patients over some time for a particular outcome of interest among groups of exposed and unexposed groups.

d. Surveillance of Acute Flaccid Paralysis in Nigeria

e. All the options listed above are true.