Final answer:
Ethanol is more likely to be a liquid than dimethyl ether because it can form hydrogen bonds resulting in stronger intermolecular forces and a lower vapor pressure, which indicates a higher boiling point.
Step-by-step explanation:
Between ethanol (C₂H₅OH) and dimethyl ether (CH₃OCH₃), ethanol is more likely to be a liquid at a given temperature. Comparing their intermolecular forces (IMFs), ethanol exhibits both London dispersion forces and the ability to form hydrogen bonds, whereas dimethyl ether primarily exhibits London dispersion forces due to its smaller dipole moment.
Ethanol's ability to form hydrogen bonds provides stronger overall IMFs which means fewer molecules escape from the liquid, resulting in a lower vapor pressure than dimethyl ether. This translates to a higher boiling point for ethanol (about 79°C) compared to dimethyl ether's significantly lower boiling point (around -25°C). Therefore, ethanol will more readily exist in the liquid state under the same conditions.
The answer to the question is A. Ethanol.