Task: Question Answering
Input (English): Background Paragraph: Vapor pressure is a measure of the pressure exerted by a gas above a liquid in a sealed container. While viscosity and surface tension increase as the strength of intermolecular forces increase, vapor pressure decreases . This is because the stronger the intermolecular forces are, the harder it is for liquid molecules to escape into the gas phase. Vapor pressure a measure of how much of a substance is in the gas phase when that substance is at equilibrium; that is, the number of molecules in the gas and liquid phases are not changing. The more molecules that are able to escape into the gas phase, the higher the vapor pressure. Vapor pressure is also proportional to temperature. As temperature increases, vapor pressure also increases. 
Story: As a part of his engineering job Keith is measuring the vapor pressure of two locomotives, engine A and engine B. 
Engine A has a high vapor pressure, but engine B has a low vapor pressure. He noticed that to increase the speed of the engines he needed to increase the vapor pressure. 
Question: Which engine's liquid would have weaker intermolecular forces, engine A or engine B?
Output (English): engine A.