Answer :
Ethanol and acetone have flash points less than 99.8 degrees Fahrenheit, while glycerin does not; water's flash point is irrelevant as it is non-flammable. Thus, 2) Ethanol and 3) Acetone are the correct answers.
The flash point of a liquid is the lowest temperature at which it can vaporize to form an ignitable mixture in air. Ethanol has a vapor pressure of 0.178 atm at 40 degrees Celsius (104 degrees Fahrenheit), which suggests it is volatile and has a low flash point. Similarly, acetone and diethyl ether are known to be flammable and highly volatile with low flash points.
Glycerin, on the other hand, is essentially nonvolatile at moderate temperatures and would not have a flash point below 99.8 degrees Fahrenheit. Water's flash point is not applicable since it does not catch fire.
Among the given liquids, ethanol (C2H5OH) and acetone have flash points less than 99.8 degrees Fahrenheit.