Which of the Following Is an Example of Explanatory Research

Which of the following is an example of explanatory research?

A) a research project found that a program intended to reduce violence needed more financial support to carry out the project effectively
B) a researcher conducted intensive interviewers with research participants to explore an aspect about school shootings that had not been conducted before
C) a research project reported a higher prevalence of violence during certain ages than others
D) a researcher who found that teens who have witnessed violence in the past are more likely to be victims and/or perpetrators of violence in the future