For Which of the Following Situations Is the Observation Method

For which of the following situations is the observation method of gathering research data best suited?

A) estimating the number of people who will attend a Bruce Springsteen concert
B) determining how many packets of ketchup the average person uses on a regular order of fries
C) finding out what radio stations people listen to when they are stuck in a traffic jam
D) determining how many people accessed a company through its Web site
E) estimating the number of people who borrow books from a library each month