Can cell phone use lead to brain cancer?


Which technique would represent the MOST cost effective approach to conduct an investigation of this research question?
A) Do a literature review on previous studies done on this topic.
B) Ask friends and family that use cell phone if they have brain cancer.
C) Call the cell phone companies and talk to a customer service representative.
D) Hire a research firm to write, distribute, collect, and analyze results of a national survey.