Answer:
5th
Step-by-step explanation:
Systematic sampling is a method of sampling probability in which samples are being selected from a larger population after picking a starting point at a fixed, periodic interval known as the sampling interval. The sampling interval is calculated by dividing the population size by the desired sample size.
Since they are 250 clients and we need to select 50 clients using systematic sampling. After a random starting point has been chosen the researcher should select every 5th client(250 / 50) on the list.