What is the proper number of spaces following a sentence-ending punctuation mark?

The proper number of spaces following a sentence-ending punctuation mark has evolved over time, particularly with the transition from typewriters to word processors. The traditional practice was to insert two spaces after a period at the end of a sentence. This was primarily because typewritten text had fixed-width fonts, and the extra space helped to visually separate sentences, making the text easier to read.

However, in modern typing and word processing, the standard has shifted toward using one space. This change is often highlighted in style guides and educational materials, reflecting the advancements in technology and the adoption of proportional fonts where the width of letters varies. As a result, the use of one space after a sentence-ending mark is recommended for most contemporary writing styles.

In this context, the answer identified as correct, which promotes the use of two spaces, aligns with the historical practice that some still follow, although it may not be the current standard in many writing environments. Understanding this practice is important for those learning and applying keyboarding skills, as it can impact the professionalism and readability of their written communication.