Claude DuPere Has a List of Measures on the French

Claude DuPere has a list of measures on the French influence in the New Orleans area. He asked you to identify the one that is NOT an unobtrusive measure. Which one is it?

A) the wear on novels in the New Orleans Public Library written in French
B) walking down a street in New Orleans and noticing that most of the signs in stores in a neighborhood are in French or French-Cajun
C) a list of votes supporting bills on bilingual education in the Louisiana state legislature with the area represented by each legislator noted on the list
D) a box of 300 letters written by people living in New Orleans to relatives living in French-speaking areas outside the state (e.g., Quebec) between 1980 and 1985
E) a survey using a three-page questionnaire partly written in French that was distributed to residents of a neighborhood