Parallel venation is found in:

Hint: It plays an important role in the process of respiration by receiving the blood that is oxygenated in the alveoli (hollow air sacs) and then returned into the left atrium. Oxygen enters in blood while carbon dioxide leaves the blood and exhales out of the body.

Complete step by step answer:
Venation is the pattern or arrangement of veins or veinlets on a lamina or leaf blade. There are two types of venation found: reticulate venation and parallel venation. Parallel venation is found in those flowering plants whose seeds contain only one embryonic leaf.
When veins are arranged parallel to one another over the leaf blade or lamina of the plant is known as parallel venation. Parallel venation is found in monocot plants. Monocots are those flowering plants in which seeds contain only one cotyledon or embryonic leaf. Examples are bamboo, banana, grass, maize and wheat.

Thus, the correct answer is Monocot Plants

Additional information: Due to the presence of mid veins, the parallel venation is divided into 2 types.
1. Pinnate parallel venation: In this type of parallel venation, veins arise from the midrib that is present in the centre of the leaf lamina from the base to apex. Veins grow perpendicular to midrib and parallel to one another. Pinnate venation is also known as the unicostate parallel venation. For example: banana.
2. Palmate parallel venation: Palmate parallel venation is a type of parallel venation in which veins are present and they are parallel to one another. It is also known as multicostate venation. For example: grass.

Note:
Palmate venation is further divided into two types i.e. convergent palmate and divergent palmate. Parallel venation is found in monocot plants and it is the characteristic feature in them. But there are few exceptions like there are few dicot plants that exhibit parallel venation like Eryngium and Calophyllum.