The most volatile of the given liquids is A. Ether B. Liquid C. Liquid NH3 D. Liquid He

The correct answer is D. Liquid He.

Volatile liquids have a low boiling point and evaporate easily. This means that they have a high vapor pressure, which is the pressure exerted by the vapor of a liquid in equilibrium with its solid or liquid phase. The vapor pressure of a liquid increases

Ether, liquid C, and liquid NH3 are all liquids with relatively high boiling points. This means that they have relatively low vapor pressures and do not evaporate easily. Liquid He, on the other hand, has a very low boiling point and a very high vapor pressure. This means that it evaporates very easily.

Therefore, the most volatile of the given liquids is liquid He.