In a Recent Study by Goldstein and Colleagues (2008),which of the Following

In a recent study by Goldstein and colleagues (2008) ,which of the following techniques proved to be most effective as getting hotel guests to reuse their bath towels?

A) putting a sign in every room stating "Help Save the Environment" with a cute endangered animal on it
B) having hotel clerks ask guests face-to-face to reuse towels
C) offering a free breakfast to guests who reused their towels two nights in a row
D) putting a sign in the room stating that that majority of guests in this room reuse the towel