Give the name of the kind of sampling that was most likely used in each of the following cases:
a. A Wall Street Journal poll of 2,000 people to determine the president’s approval rating
b. A poll taken of each of the General Motors (GM) dealerships in Ohio in December to determine an estimate of the average number of Chevrolets not yet sold by GM dealerships in the United States
c. A quality-assurance procedure within a Frito-Lay manufacturing plant that tests every 1,000th bag of Fritos Corn Chips produced to make sure the bag is sealed properly
d. A sampling technique in which a random sample from each of the tax brackets is obtained by the Internal Revenue Service to audit tax returns