Which of these is an example of a non-random sample?
a.
a cereal company surveys their employees about breakfast food preference.

b.
a farmer is choosing grains of wheat from a field to test for a new flavor of cereal.

c.
ten college students at a college, population 50,000, are chosen to taste test a new cereal.

d.
a cereal company puts a winning ticket in one box of cereal out of 100,000 boxes.