Which of the following plants possesses sunken stomata?

Thermo-regulation in dogs takes place by

Choose the correct option:
$(1)$ On an average,a healthy human breathes ...$X$... times/minute.
$(2)$ Every $100 \, ml$ of oxygenated blood can deliver around ...$Y$... of $O_2$ to the tissues under normal physiological conditions.
$X-Y$

$A$ : The passage starting with the external nostrils up to the terminal bronchiole constitutes the respiratory part.
$R$ : The respiratory part transports the air to the alveoli,clears it from foreign materials,humidifies it,and brings the air to body temperature.

The maximum amount of water vapour that the atmosphere can hold at a given temperature is known as:

The scientist who proposed that the production of glycolic acid in guard cells is an important factor in stomatal opening is: