Copious is to amount as spacious is to what?

The reasoning behind selecting "extent" as the answer relates to the definition and contextual use of the words involved. "Copious" refers to a large quantity or abundance of something, highlighting the idea of a significant amount or a high degree of abundance. Similarly, "spacious" refers to a large area or ample space, which pertains to the physical dimensions of a place.

In this analogy, just as "amount" describes the quantity aspect of "copious," "extent" describes the dimensional aspect of "spacious." Both terms establish a relationship where the first word denotes a quality (in this case, quantity or dimension), and the second word relates directly to that quality.

The other options don't align as closely with the relationship established by "copious" and "amount." "Mass" typically refers to the quantity of matter in an object, which doesn't directly translate to the concept of physical space. "Quality" is a broader term that encompasses characteristics but does not specifically address the idea of size or area. "Motion" describes movement, which is unrelated to the concept of space as defined by "spacious." Thus, "extent" best captures the relationship similar to that of "copious" to "amount."