Which of the Following Is a Reason It Is Difficult

Which of the following is a reason it is difficult to assess if gangs--such as the Mara Salvatrucha (MS-13) and 18th Street (M-18) --are actually spreading across the country?

A) The media does not report on the presence of these gangs.
B) It is challenging to parse out gang activity from broader immigration patterns.
C) There is little investigation into the actual presence of these gangs across the country.
D) These gangs are of little concern to law enforcement outside of Los Angeles.