The correct option is C respirometer
Respirometer is an instrument used for measuring rate of respiration. The apparatus consists of a graduated tube attached at right angles to a bulbous respiratory chamber in its upper end. Desired plant material whose rate of respiration is to be determined is placed in the respiratory chamber.
Speed is measured using a speedometer.
Manometer is used to measure pressure of liquids or gases.
Barometer is used to measure atmospheric pressure.