ANS:B - isothermal

An approximately isothermal process exemplifies the flow of a gas through a very long pipe of uniform cross-section. In an isothermal process, the temperature remains constant. When a gas flows through a very long pipe of uniform cross-section at a constant temperature, heat exchange occurs between the gas and the surroundings such that the temperature of the gas remains constant. This leads to an approximately isothermal process. The other options do not specifically describe the conditions of flow through a very long pipe with a uniform cross-section:

• Adiabatic: This process describes a situation where there is no heat exchange between the system and its surroundings.
• Isentropic: This process describes a reversible adiabatic process with no entropy change.
• Isochoric: This process describes a situation where the volume remains constant.