For each of the following situations, would you recommend\ a sample or a census? Explain your reasoning in each case.
a. A purchasing agent has just received a shipment of shock-resistant watches and wants to find out approximately how far they can be dropped onto a concrete surface without breaking the crystal.
b. General Mills wants to learn the age, gender, and income characteristics of persons who consume Cheerios breakfast cereal.
c. The producers of NBC's Tonight show want to find out what percentage of TV viewers recognize a photo of host Jay Leno.
d. A small company wants to determine whether U.S. companies that manufacture nuclear submarines might be interested in a new technique for purifying air when such craft are submerged.