Which of the following is an example of an ascender?

An ascender is a part of a lowercase letter that extends above the x-height of the font. In the context of the provided choices, the letter 'k' serves as an example of an ascender because its stem rises above the x-height. This distinctive feature makes 'k' a prime representation of letters with ascenders.

For a better understanding, consider the characteristics of the other letters. The letter 'g' typically has a descender, which is a part that goes below the baseline. The letter 'd' does indeed have an ascender, but it is not the selected answer here. The letter 'o' is a rounded shape that resides entirely within the x-height and has no ascender or descender. Recognizing these distinctions helps in understanding the classification of different letter forms in typography.