Pls answer

Dear student.

A: Midrib.
B: Vein
C: Lamina
D: Petiole.

Midrib is the thickest central vein present in the middle of lamina of leaf. From midrib arises many lateral veins.
It performs following functions:

• Midrib along with lateral veins forms leaf's skeleton and provides mechanical support to leaf
• It also helps to transport water, minerals to different cells of leaf  
• It transports synthesised food from leaf to stem wherefrom it is carried to different parts of plant.

Petiole is the stalk of the leaf which attaches the lamina to the stem.

Regards.