What is a problem with the design of the following experiment: A restaurant wants to know if their customers like their newest dish. 30 customers tried the dish, while the majority tried another dish. They surveyed the first 20 people to leave the restaurant. 5 people responded that they enjoyed the new dish, 1 responded that they did not, and 14 responded that they did not know.
A. Not surveying customers while they were eating
B. Waiting until the customers were leaving the restaurant
C. Surveying only 20 people, rather than all customers in the restaurant
D. Surveying the first 20 customers who left the restaurant, rather than those who tried the new dish