Which statement gives a quantitative observation?

Correct answer: The plant is twenty centimetres tall

The direct answer is D: the plant is twenty centimetres tall. A quantitative observation includes a number or a measurable amount, often with a unit. The statement gives the numerical value twenty and the unit centimetres, so the plant’s height is expressed quantitatively. Step by step: identify what is observed, measure it, write a number, and attach an appropriate unit. Option A, “the water is cold,” is mainly qualitative because it describes a quality without stating a temperature. Option B, “the leaf is beautiful,” is a personal judgement and is not a precise scientific measurement. Option C, “the flower has a strong smell,” is also a qualitative description; different people may judge “strong” differently unless intensity is measured by a defined method. Option D is correct because height is measured numerically in centimetres. A quantitative observation can be checked and compared more easily than a vague description. Memory cue: quantity means “how much”; look for a number and a unit.