Final answer:
Proofing mandrels and swabs are used to check for obstructions in the raceway system.
Therefore, the correct answer is: option d).obstructions
Step-by-step explanation:
Proofing mandrels and swabs are used in engineering to ensure that raceway systems, which protect electrical conductors, are free of obstructions.
These tools are inserted into the raceway to ensure that there are no blockages that could hinder the flow of a substance, such as air, gas, or liquid, through the system.
For example, in an industrial setting, proofing mandrels and swabs may be used to check the interior of pipes or tubes for any debris or foreign objects that could cause clogs or damage.
It is essential to regularly inspect the raceway system and address any obstructions promptly to maintain a smooth and efficient flow.