Final Answer:
The fluid measurement type that returns a percentage of the viewport width is vw (Option B).
Step-by-step explanation:
In web design, fluid measurements are used to create responsive layouts. Among the options provided:
px (pixels) is an absolute unit.
em is relative to the font-size of its closest parent or the element itself.
vh (viewport height) is a percentage of the viewport height.
The correct option is vw (viewport width), which returns a percentage of the viewport width. For example, if an element is set to width: 50vw, it will be 50% of the viewport width, adjusting dynamically as the viewport size changes.
Option B is the answer.