Final answer:
A page of plain text is approximately one kilobyte (KB) in size, which is answer A. It equates to about 180 English words or less than half of a single-spaced typed page.
Step-by-step explanation:
The size of a big file is a page of plain text (.txt) can vary based on the content, but generally, a page of plain text is approximately one kilobyte (KB). Given that one KB equates to 1,024 bytes, and considering that this is roughly equal to 180 English words or less than half of a single-spaced typed page, the correct answer is A. Approximately 1 kilobyte (KB). Remember that a megabyte (MB) consists of 1,024 KB, so a page of plain text is nowhere near as big as an MB.