Communicable diseases
a. are also known as noninfectious diseases.
b. can only be caught from coughs and sneezes.
c. are caused by lifestyle choices, such as smoking cigarettes.
d. are caught from food, water, animals, another person, or something else in the environment.

The answer is letter D.

Communicable diseases are also known as infectious or contagious diseases. They may come from food, water, animals, another person, or anything that comes from the environment. Airborne viruses, bacteria, blood, and bodily fluids can cause the spread of these diseases. The most common communicable disease is the flu, which can easily spread in an enclosed environment with a recycled circulating air (e.g. air-conditioning). Infectious disease caused by blood contact like HIV/AIDs are also dominant in society.   

Ican only answer your first question, a machine is like a human body because it's a little similar. they both almost work like the same.

True your body needs vitamins such as protein, vitamin d, fish oil etc