This is a test of commonsense with single/multi-choices. Complete the next sentence:

How to know if you have a stomach virus
Understand the symptoms of a stomach virus or flu.
This illness affects each area of the gastrointestinal tract. Its symptoms can include nausea and vomiting, diarrhea, abdominal discomfort, and general malaise.

Possible answers:
(1). Note any unexplained negative discomfort. Despite symptoms' similarity to regular nausea and vomiting, never feel ill from this virus.
(2). Symptoms include : Nausea: queasiness or nausea, redness or sore throat. A feeling of fullness around the stomach, which may be something just a little beyond discomfort.
(3). You may have one or all of the symptoms if you have a stomach virus. The illness is self limited, meaning the virus usually runs its course in 2-3 days.
(4). It is harder to diagnose if you have a stomach virus than if you have a flu. This ailment is usually classified as an infection.
The answer is:
(3).