Since they are talking about brand recognition and popularity, I would say D. perception accounts for mediocre products trumping quality. People go with the product they know or they think more people are using because it is perceived as a better product even though it may not be.
D neither a nor b is right
Answer: Public health measures such as pure food and water, and development of immunizations against many serious diseases such as polio and smallpox, coupled with enhanced economic conditions, are together credited with substantial reductions in the burden of infectious diseases.
I think C. Hopefully I helped, health is not really my forte