Which of the Following Is NOT a Likely Reason Why

Which of the following is NOT a likely reason why diseases caused by opportunists are becoming more frequent in the U.S.population?

A) HIV individuals (with impaired immune systems) survive longer due to more effective therapies-but this allows them a longer period of time to be infected by opportunists.
B) Individuals in the United States are living longer than ever before-but they're living with a number of chronic health issues that can impair the immune system.This leads to a greater likelihood of opportunistic infections.
C) Cancer treatments have improved significantly in the last 30 years-but they often suppress the immune system.This leads to a greater likelihood of opportunistic infections in such individuals.
D) Travel into and out of the United States has increased significantly.This has the potential to bring in many new pathogens that can cause new infections,even in otherwise healthy and immunocompetent individuals.