The answer is to your question is A
The correct answer is option C, that is, viruses.
An infection occurs when a foreign species moves inside the body of an individual and causes harm. The species utilizes the body of that person to reproduce, sustain itself, and colonize. These infectious species are called pathogens. The examples of pathogens are viruses, bacteria, prions, and fungi.
Of the given options, viruses are the smallest infectious agent. The viruses are basic particles, which must infect a host cell to reproduce and develop. Viruses utilize the host cells metabolic machinery to double themselves.
Answer;
The large intestine is much wider than the small intestine, but it is also much shorter. The small intestine is the longest part of the digestive system.
Explanation;
The small intestine is a muscular tube with three parts; the duodenum breaks down the food, the jejunum and the ileum absorb nutrients and send them into the bloodstream.
The reason why the small intestine is longer than the large intestine and any other part of the digestive system is to ensure maximum and complete absorption of nutrients to the blood stream.
The correct answer is option 
.
The is an ion made up of two atoms nitrogen and hydrogen.
The polyatomic ions are those ions, which are formed by the binding of the two or more elements, which has a charge and act as an ion. As all others are formed by a single atom, they are not polyatomic, only is formed by two atoms, hence, it is an polyatomic ion.
Answer:
B. Ethanol
Explanation:
During absence of O2 pyruvic acid is reduced to ethanol in alcoholic fermentation.
