Which of the following best describes the hydrophobic tails of phospholipids?

The correct choice is that the hydrophobic tails of phospholipids are water-repelling. This characteristic is fundamental to the structure of phospholipids, which are key components of cell membranes.

Phospholipids consist of a hydrophilic (water-attracting) head and two hydrophobic (water-repelling) tails. The tails are typically composed of long fatty acid chains, which do not interact favorably with water. This hydrophobic nature means that in an aqueous environment, phospholipids will organize themselves into a bilayer structure, with the hydrophilic heads facing outward towards water and the hydrophobic tails tucked away from the water in the interior of the membrane. This arrangement is crucial for forming a stable cellular barrier, influencing membrane fluidity, and allowing for various functions such as signaling and transport.

In contrast, the other options do not accurately describe the properties of the hydrophobic tails. They do not attract water, nor are they soluble in it. Additionally, while they can play a role in interactions with other molecules, describing them as highly reactive with sugars is misleading and not characteristic of their fundamental nature.