Which of the following character sets is commonly used alongside ASCII for presenting data?

The choice of Unicode as the character set commonly used alongside ASCII for presenting data is particularly relevant due to its design to be a comprehensive standard for text representation across different languages and symbols. ASCII, which includes only 128 characters, is limited in its ability to represent the vast array of characters needed for global communication. Unicode expands this capability by providing a unique number for every character, no matter the platform, program, or language. This allows for consistent representation and manipulation of text in diverse applications.

While UTF-16 is a form of Unicode that encodes characters in either 16 or 32 bits, it is more specialized and not as universally recognized as Unicode itself. Base64 is an encoding scheme primarily used for data transfer and does not focus on character representation. ISO-8859-1 is an extension of ASCII that includes additional characters for Western European languages but is still limited compared to the comprehensive nature of Unicode. Thus, Unicode is the most encompassing and commonly used alongside ASCII when presenting data, making it the correct choice.