Which of the following resolutions is categorized as standard definition?

Standard definition (SD) is typically associated with a resolution of 640x480 pixels. This resolution is part of the older television broadcast standards. It is considered lower quality compared to newer high definition formats.

In contrast, the other resolutions mentioned represent higher definitions. For instance, 1280x720 is classified as HD (high definition), while 1920x1080 is known as Full HD (FHD). The 2560x1440 resolution falls under Quad HD (QHD) and is considered even higher than Full HD, offering greater detail and clarity. Thus, the resolution of 640x480 is specifically recognized as standard definition due to its historical usage and pixel count in comparison to these progressive high definition standards.