Which of the following samples would constitute a biased sample?

Seventh grade girls were randomly surveyed to determine what theme the whole school would prefer for the dance.
A tele-market research company randomly called and surveyed one thousand men and women over the age of 65 to determine which insurance companies were preferred in retirement.
Kids at a large preschool were randomly surveyed to determine the color most preschoolers like best at that school.
Two thousand people were randomly surveyed about their favorite candy in four different cities in Arizona to determine Arizona’s favorite candy.

Seventh grade girls were randomly surveyed to determine what theme the whole school would prefer for the dance.

Step-by-step explanation:

-This method of sampling is systematically different from the population( whole school).

-It favors some outcomes over the others. Seventh grade preferences have a 100% chance of being played over other grade's preferences.

-The sample only truly represent's seventh grade as opposed to the whole school.

step-by-step explanation:

you divide the denominator by the numerator on both sides and if the quotients are equal then the fractions are equivalent

its a straight line parallel to the time axis