In a county that does not require measles vaccination, a preschool experienced a prolonged measles outbreak among its students beginning in September 2016 through December 2016.

Which of the following types of quantitative data collection methods could be used to find the denominator to calculate cumulative incidence of measles for the outbreak at the preschool?

Request data from the State Demography Office on the number of children of preschool age in the county at the last decennial census in 2010.

Collect records from the daycare staff on enrollment, attendance and vaccination status for each child that attended in September 2016.

Send staff to the daycare in December of 2016 to count the number of children.

Interview all parents on their child's vaccination status and dates of attendance in September of 2016.