Final answer:
A bight is best described as bending one end of the rope back upon itself, keeping the two sides parallel, and is essential in understanding rope mechanics and tension.
Step-by-step explanation:
The term bight in the context of rope work refers to Option C: Bending one end of the rope back upon itself, while keeping the two sides of the rope parallel. This is a common term used when handling ropes, and is related to the concept of tension, which is a force along the length of a flexible medium, such as a rope or cable. A bight can be involved in creating knots or loops, and is an essential concept in understanding the mechanics of ropes under tension.