In each case, indicate what sampling method was used
a) Every 4th person in the class was selected
b) A sample was selected to contain 25 men and 35 women
c) Viewers of a new show are asked to vote on the show's website
d) A website randomly selects 50 of their customers to complete a satisfaction survey
e) To survey voters in a town, a polling company randomly selects 10 city blocks, and interviews everyone who lives on those blocks.