Which of the Following Is NOT a Likely Reason Why

Multiple Choice

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

A) People with impaired immune systems such as those with HIV disease survive longer due to more effective therapies, but this gives them a longer period of time to be infected by opportunists.
B) People in the U.S. 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 people receiving these treatments.
D) Travel into and out of the U.S. has increased significantly. This has the potential to bring in many new pathogens that can cause infections, even in otherwise healthy and immunocompetent individuals.
E) People in the U.S. are living longer than ever before, but their immune systems decline with age. This leads to a greater likelihood of opportunistic infections, especially if they receive any kind of invasive procedure.