The Author Postulates a Greater Use of Triangulation in Order

The author postulates a greater use of triangulation in order to improve research quality in comparative politics. What is triangulation? Please select all that apply.

A) To explore the same data with several alternative theories.
B) To explore several forms of data with one underlying theory.
C) To explore several forms of data with several alternative theories.
D) To explore the same data with one single theory.