Concept:Quantitative data is numerical information that can be measured or counted.
Explanation:Quantitative data represents values that have numerical meaning.
It can undergo mathematical operations such as addition, subtraction, and comparison.
Length is a measurable quantity, so it is quantitative.
Colour, gender, and marital status describe qualities or categories, not numbers.
Hence, among the given options, only length qualifies as quantitative data.
Answer:D. Length