A, B, C and D are volatile liquids. The order of volatility is A > C > B > D. Now, at a particular temperature:
Volatility is the tendency of a substance to vapourize. Volatility is directly related to a liquid's vapour pressure. More volatile liquids have a higher vapour pressure. At a given temperature, a substance with higher vapour pressure vaporizes more readily than a substance with a lower vapour pressure. Now, volatility order is: A > C > B > D. So, order of vapour pressure will be: A > C > B > D.