Given is the diagrammatic sketch of a certain type of connective tissue. Identify the parts labeled A, B, C, and D and select the right option about them

A. Part-A: Mast cell; Part-B: Macrophage; Part-C: Fibroblast; Part-D: Collagen fibres
B. Part-A: Macrophage; Part-B: Collagen fibres; Part-C: Fibroblast; Part-D: Macrophage
C. Part-A: Macrophage; Part-B: Collagen fibres; Part-C: Fibroblast; Part-D: Macrophage
D. Part-A: Macrophage; Part-B: Fibroblast; Part-C: Collagen fibres; Part-D: Mast cell

Hint: Connective tissue is a type of animal tissue that allows the separation, binding, and supporting the other tissues, and also provides insulation as it is covered by an extracellular matrix and allows the transport of many substances.

Complete step by step answer: Macrophages are a type of white blood cells that take part in the immune system as they can kill the pathogen by phagocytosis. During the leukocyte extravasation, the monocytes in the blood can undergo changes and form specific types of macrophages based on the tissue or organ it is present and these macrophages are matured to perform their phagocytic action. These location-specific macrophages phagocytose the dead cells that are acted upon by the neutrophils at first, and the cytokines secreted by the irregularly shaped macrophages allow the activation of adaptive immunity. Fibroblasts in the connective tissue synthesize collagen and an extracellular matrix that provide protection and support for the animal tissues and have branched cytoplasm and has a large number of rough endoplasmic reticulum and are spindle flat cells and mainly present as parallel clusters.
Collagen fibres are long, unbranched fibres that have high tensile strength and resist stretching as they provide protection and structural support to the connective tissue and other surrounding tissues. They have collagen protein that is responsible for the elasticity in bone, tendons, and ligaments.
The mast cells in connective tissue have many cytoplasmic granules consisting of histamine and heparin that are released histamine on an inflammatory response which causes vasodilation and increased blood flow at a site of injury or infection, and an allergic response.
Hence, the correct answer is option (D).

Note: Connective tissue are mainly of three types such as connective tissue proper, supportive tissue, and fluid tissue while loose connective tissue proper includes adipose tissue, areolar tissue, and reticular tissue.