External respiration refers to the exchange of gases between which of the following?

Water vapor exits from the leaves of terrestrial plants through open stomata. During photosynthesis,carbon dioxide enters the plant through the same open stomata. Identify the reason for the above statements from the following options.

The diagram below represents part of a capillary in a specific region of the human body. The region labeled $X$ represents part of

Exchange of gases in lungs occurs through

Select the correct option for the shape of guard cells in stomata.

	Stomata of Monocots	Stomata of Dicots
$A$.	Bean-shaped	Dumbbell-shaped
$B$.	Dumbbell-shaped	Bean-shaped
$C$.	Bean-shaped	Bean-shaped
$D$.	Dumbbell-shaped	Dumbbell-shaped

The figure given below shows a small part of human lung where exchange of gases takes place. Select the option which represents labelled part ($A, B, C$ or $D$) correctly identified along with its function.