A video store employed a statistician to determine what percentage of the city's 30,000 residents shopped in the store at least once a week.

A video store employed a statistician to determine what percentage of the city's 30,000 residents shopped in the store at least once a week. The statistician decided to conduct a random survey of people in the mall in which the video store was located. Of 1000 surveyed, 500 said they shopped in the store at least once a week. The statistician concluded from this that 15,000 of the city's residents shopped in the store at least once a week.

The results of this survey were unreliable. Which is the most important reason for its unreliability?

A. The survey should have been conducted within the video store itself.

B. The survey shouldn't have been taken in the mall.

C. Random surveys are unreliable.

D. The survey would have been better if the statistician had spoken to all residents of the city.

E. The number of people surveyed was too small.