Final answer:
The type of sampling used in the given scenario is stratified sampling.
Step-by-step explanation:
The type of sampling used in the given scenario is stratified sampling.
Stratified sampling is when the population is divided into distinct groups or strata based on certain characteristics, and then a sample is randomly selected from each stratum. In this case, the population is the participants of the online survey, and the stratum is individuals aged 18-24 who indicate they are African American or Black. The survey collects demographic information from all participants, but only selects individuals from this specific stratum to continue with further survey questions.