Operators collect data during a specified manufacturing step whenever a data card is present in the work folder.

When would this be considered a valid random sampling process?

A$)$ Production Control places this data card in every $5$ th work folder

B$)$ Production Control places this data card in work folders approximately $10\%$ of the time following no specia order or pattern

C$)$ Manufacturing Engineers place this data card in work folders whenever they see operators slacking off

D$)$ Production Control places this data card in the first folder of every day