The direction wind is determined by

Step 1: Analyze the question The question asks which instrument is used to determine the direction of the wind (not its speed or any other property).

Step 2: Review each instrument

• Anemometer: measures wind speed (or force), not direction.
• Secchi disc: a circular disc lowered into water to measure water transparency (turbidity). It is used in aquatic ecology.
• Wind vane: has a pointer that swings to show the direction from which the wind is blowing. This matches the question.
• Barometer: measures atmospheric pressure.

Step 3: Identify the answer The instrument that shows wind direction is the wind vane, which is option C.

Exam tip: Match each instrument to what it measures:

• Anemometer → Air speed
• Barometer → Bar (pressure)
• Wind vane → direction
• Secchi disc → water clarity
• Hygrometer → humidity
• Thermometer → temperature

Biology ecology questions often test these instruments, so learning them as pairs is a quick way to gain marks.