Explanation:

- Sphygmomanometer: This is the correct instrument used to measure blood pressure. It consists of an inflatable cuff to restrict blood flow and a mercury or aneroid manometer to measure the pressure.

Option: 1, Sphygmomanometer is the correct answer.

- Lactometer: This is used to measure the specific gravity of milk, which helps determine purity.

- Thermometer: This device measures temperature, typically body temperature.

- Glucometer: This is used for measuring blood glucose levels, helpful for diabetic patients.

Each of these instruments serves a specific purpose in medical or scientific measurements.