Which Description Is the BEST Example of Naturalistic Observation Research

Which description is the BEST example of naturalistic observation research methodology?

A) recording the attractiveness level of women approached by men at the bar
B) asking men to rate the attractiveness level of female faces while either sober or intoxicated
C) surveying university students about the qualities that they find attractive in a possible romantic partner
D) randomly assigning participants on first dates to either a hike in the woods or a city tour and then surveying their attitudes towards their partner