Question

1. air vents on radiators:

image of an air vent on a radiator

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• are on two pipe systems
• are at the top of the radiator
• allow steam to escape
• may be stuck open
• are needed on every other radiator

1. common problems with

Explanation:

To determine the correct answer, we analyze each option:

• Option "Are on two pipe systems": Air vents on radiators are typically on one - pipe steam systems (where steam goes to the radiator and condensate returns), not two - pipe systems in the context of their main placement logic for air release.
• Option "Are at the top of the radiator": Air is less dense than water or steam. In a radiator, especially in steam or hot - water heating systems, air accumulates at the top. So air vents are installed at the top to allow air to escape, which is a fundamental principle of their design and function.
• Option "Allow steam to escape": Air vents are designed to let air out, not steam. They have mechanisms (like a float or a thermostatic element in some cases) that close when steam or water reaches them, preventing steam from escaping.
• Option "May be stuck open": While a stuck - open air vent is a possible problem, it is not a defining characteristic of what air vents on radiators are (their basic design/placement/function).
• Option "Are needed on every other radiator": Air vents are needed on each radiator (or at least in the heating system setup) to ensure proper air removal for efficient heating, not every other one.

Answer:

B. Are at the top of the radiator