Which observation is made using a sense organ?

Correct answer: The bell sounds loud

The direct answer is A: the bell sounds loud. An observation made with a sense organ uses hearing, sight, smell, taste, or touch. Hearing tells us that a sound is loud or soft. Option A is correct because the loudness of the bell is noticed directly by the ears and is a qualitative description. Option B gives a mass of two kilograms; this requires a balance, so it is an instrument-based quantitative measurement, not simply a sense-organ observation. Option C gives a length of thirty centimetres; a ruler is needed. Option D gives a duration of ten seconds; a clock or stopwatch is needed. Notice that “loud” is a descriptive quality, whereas the other three options give numerical measurements. Memory cue: ears hear sound; rulers measure length; balances measure mass; clocks measure time.