Since the 1970s, approximately 40 new infectious disease agents have been discovered, including SARS, chikungunya and zika. The ability of these agents to spread rapidly and cause global concern is due to all of the following except .a. communities are becoming more densely populated. b. communities are becoming more sparsely populated. c. individuals are traveling more frequently and farther distances than in the previous half-century. d. communities are spreading into rural areas/wildlife habitats.

Letter b

Explanation:

The diseases that are common to wild species are becoming more prone to be human diseases since the 1970s. Virus are specially important agents of sources of disease because their nature allows them to spread and adapt to different hosts easily compared to other organisms. After the 1970s the urbanization rate around the world has accelerated and thus most part of the world population it is now allocated on those dense populated areas. Those areas tend to be easy targets for a spreading infectious disease that culminate in global threats.

some inherited genetic mutations can be good for the offspring, so the answer is different genetic mutations cause many forms of cancer.