In this task, you are given a question and a context passage. You have to answer the question based on the given passage.

[EX Q]: What is a prerequisite for weight to play a factor in conductivity?, Context: While inert gas reduces filament evaporation, it also conducts heat from the filament, thereby cooling the filament and reducing efficiency. At constant pressure and temperature, the thermal conductivity of a gas depends upon the molecular weight of the gas and the cross sectional area of the gas molecules. Higher molecular weight gasses have lower thermal conductivity, because both the molecular weight is higher and also the cross sectional area is higher. Xenon gas improves efficiency because of its high molecular weight, but is also more expensive, so its use is limited to smaller lamps.
[EX A]: constant pressure and temperature

[EX Q]: Which element is mentioned?, Context: Breathing pure O2 in space applications, such as in some modern space suits, or in early spacecraft such as Apollo, causes no damage due to the low total pressures used. In the case of spacesuits, the O2 partial pressure in the breathing gas is, in general, about 30 kPa (1.4 times normal), and the resulting O2 partial pressure in the astronaut's arterial blood is only marginally more than normal sea-level O2 partial pressure (for more information on this, see space suit and arterial blood gas).
[EX A]: O2

[EX Q]: What's on the line in Maine?, Context: Amtrak's Northeast Corridor and Chicago lines originate at South Station, which serves as a major intermodal transportation hub, and stop at Back Bay. Fast Northeast Corridor trains, which serve New York City, Washington, D.C., and points in between, also stop at Route 128 Station in the southwestern suburbs of Boston. Meanwhile, Amtrak's Downeaster service to Maine originates at North Station, despite the current lack of a dedicated passenger rail link between the two railhubs, other than the "T" subway lines.
[EX A]:
North Station