Which statement best matches the given definition of one-to-one correspondence?

• A. A mapping from each element of one set to exactly one element of another set and vice versa.
• B. A set with elements that cannot be paired.
• C. Two elements can share the same value in a mapping.
• D. A process of grouping items by tens.

Answer: (A)

One-to-one correspondence means you pair up every element from one set with exactly one element from another set, and every element in the second set is paired with exactly one element from the first. This reciprocal, unique pairing ensures there are no left-out elements and no two elements from the first set share the same partner. The statement describing a mapping where each element of one set maps to exactly one element of another set and, conversely, each element of the second set is the image of exactly one element from the first, captures this precise, reciprocal relationship. The other options describe ideas that don’t fit a one-to-one pairing: some elements would be unpaired, or multiple elements would map to the same element, or the concept is unrelated to mapping.