Which of the following statements best describes what pixels, ems, and rems have in common?

The choice highlighting that pixels, ems, and rems are all units of measurement used to define the length of elements on a webpage is accurate. Each of these units serves the purpose of quantifying dimensions in web design, allowing developers to specify sizes for various properties such as width, height, margins, padding, font sizes, and more.

Pixels are absolute units that represent a specific point on the screen and are fixed regardless of the user's settings. Ems and rems, however, are relative units. Ems are based on the font size of the element they are applied to, while rems are based on the root font size of the document. This flexibility promotes responsive design, where element sizes can adjust based on user preferences or screen configurations.

The other options do not correctly reflect the nature of these units. The statement about fluid units is misleading because although ems and rems are flexible, pixels are not considered fluid as they do not scale with the user's settings. Additionally, calling them static units misses the essence of how ems and rems function. Understanding these distinctions helps clarify their roles in creating adaptable and user-friendly web designs.