Which best describes building blocks?

Answer: Collections of formatting information that can be used as the basis for a new document

Building blocks can help maintain any formatting you have applied in your document like bold, insertion of headers and footers, centering, and many other options. It allows you to create reusable chunks of content and can be used over and over again especially on some types of writing such as legal field.

system programmer option d is correct

because an operating system is software that manages computer hardware and system resources.