Final answer:
Lymphocytes are the predominant type of circulating cell in cattle, sheep, and goats; these include both B-cells and T-cells, which play key roles in the adaptive immune response.
Step-by-step explanation:
The predominant type of circulating cell in cattle, sheep, and goats is lymphocytes.
These are crucial immune cells that are involved in the body's adaptive immune response.
In the bloodstream of these animals, there are predominantly two types of lymphocytes:
B-lymphocytes (B-cells) and T-lymphocytes (T-cells).
B-cells are primarily responsible for antibody production, while T-cells perform a variety of roles, including helper functions and cytotoxic actions.
Each of these cell types originates from bone marrow and matures in different areas of the body, with T-cells maturing in the thymus.
Therefore, the correct answer to the multiple choice question is option 4) Lymphocytes.