"Triangulation" in Qualitative Inquiry Means

"Triangulation" in qualitative inquiry means

A) developing three alternatives to each null hypothesis.
B) attempting to get the observer, the observed subject, and a disinterested third party to reach consensus on the meaning of the data.
C) assessing the quality of observational data by having two observers simultaneously recording the behavior of one human subject.
D) using multiple sources of data, multiple observers, and/or multiple methods of data collection.