Question

read the passage.
flu confusion
though proven effective in flu prevention, the influenza vaccine, or \flu shot,\ wont keep you from contracting the stomach flu. this is because the name \stomach flu\ refers to a condition that is completely different from the ordinary flu, or influenza. in common parlance, \stomach flu\ typically refers to a condition called gastroenteritis, in which the digestive tract becomes irritated. there is no vaccine to prevent gastroenteritis, which may be caused by a variety of viruses, bacteria, other organisms, and certain foods. common symptoms include stomach pain, vomiting, and diarrhea. the
egular\ flu, on the other hand, results from a strain of the influenza virus. common symptoms include fever, cough, congestion, fatigue, and muscle aches. stomach upset may also occur, but this is not as common as the other symptoms.
what is the main, or central, idea of the passage?
while flu shots can help prevent influenza, they do not prevent gastroenteritis, or stomach flu.
the term \stomach flu\ is more correctly known as gastroenteritis, in which the digestive tract becomes irritated.
the flu and the stomach flu are separate conditions, each with its own causes and symptoms.

Explanation:

The passage compares the "regular" flu (influenza) and the "stomach flu" (gastroenteritis). It discusses their different causes (influenza virus vs. various viruses, bacteria, etc.), symptoms (fever, cough, etc. for regular flu; stomach pain, vomiting for stomach flu), and mentions that the flu shot only prevents influenza. The main idea should encompass the separation of these two conditions with their own causes and symptoms.

Answer:

The flu and the stomach flu are separate conditions, each with its own causes and symptoms.