The most common cell type in dense regular connective tissue is the .

Fibroblast

Explanation:

Connective tissue is the tissue which is named for its function that is the tissue which connects the two system, two tissues and two cells in a body.

The connective tissue is usually composed of a variety of cells which includes mast cells, adipocytes, macrophages and some fibres.

The fibre is the main component of the connective tissue as it provides strength to the tissue, therefore, the fibroblasts which secrete these fibres called collagen fibres and the components of the matrix form the highest composition of the connective tissue.

Thus, Fibroblast is correct.

answer; polycythemia is the correct answer;