The instrument, barometer, is used for measuring

Step 1: Analyze the question The question asks what a barometer measures. The key is knowing the weather instruments and what each one records.

Step 2: Explain the concept A barometer measures atmospheric (air) pressure. The word comes from the Greek baros, meaning "weight". Air has weight, and the barometer measures the force that the air above exerts on a surface.

The main types are:

• Mercury barometer: the height of a mercury column shows the pressure.
• Aneroid barometer: a sealed metal chamber expands or contracts as pressure changes.
• Barograph: records pressure continuously over time.

Pressure is measured in millibars (mb), hectopascals (hPa), or millimetres of mercury (mmHg). Standard sea-level pressure is about 1013.25 mb.

Step 3: Check each option

• A. Temperature: measured with a thermometer (e.g. Six's maximum and minimum thermometer). ❌
• B. Wind speed: measured with an anemometer. (A wind vane gives direction.) ❌
• C. Relative humidity: measured with a hygrometer or psychrometer (wet and dry bulb hygrometer). ❌
• D. Air pressure: measured with a barometer. ✅

Step 4: Answer The correct option is D. air pressure.

Exam tip 💡 Match each instrument to its quantity:

• Barometer → pressure (think "bar", as in millibar)
• Anemometer → wind speed
• Hygrometer → humidity (hygro means moisture)
• Thermometer → temperature
• Rain gauge → rainfall
• Sunshine recorder → hours of sunshine

WASSCE often asks this type of question, so learn these pairs and you can pick up easy marks.