GED Science Practice Test – Prep, Questions & Study Guide

Fusion, in this context, refers to the combining of images from the two eyes to form a single visual percept. This process is essential for depth perception and creating a clear, three-dimensional image of the world around us. Option A, a long narrow inlet of the sea between steep cliffs, does not relate to fusion and is more closely related to the concept of a fjord. Option C, (astronomy) a collection of star systems, also does not pertain to fusion. Option D, twins who develop from two separate fertilized eggs, may seem similar to fusion as they start as separate entities and come together, but they are still two distinct individuals and not a single visual percept. Therefore, option B is the most appropriate definition of fusion in this context.