An executive for a large national restaurant chain with multiple locations in each of 513 counties wants to personally sample the cleanliness of the chain's restaurants throughout the country by visiting restaurants. The executive wants a good-quality sample but wants to minimize travel time and expenses. Which of the following sampling methods would b most appropriate? Select the correct answer below: A. Obtain a convenience sample by visiting the 100 restaurants that are closest to the executive's office.
B. Obtain a systematic sample by selecting every 20th restaurant from a list that orders all restaurants by date of opening
C. Obtain a stratified sample by visiting I randomly selected restaurant ik every county.
D. Obtain a cluster sample by randomly selecting 20 counties and visiting every restaurant within those counties.