To solve this problem, we need to analyze each option to determine which statement is correct. Let's evaluate each one:$\newline \bullet$Option 1: Plasma = Blood – Lymphocytes$\newline$ - Plasma is the liquid component of blood, composed of water, salts, enzymes, antibodies, and other proteins.$\newline$ - Blood consists of plasma, red blood cells (RBCs), white blood cells (WBCs), and platelets.$\newline$ - Lymphocytes are a type of WBC, so subtracting lymphocytes from blood does not yield plasma.$\newline$ - Therefore, Option 1 is incorrect.$\newline \bullet$Option 2: Serum = Blood + Fibrinogen$\newline$ - Serum is the component of blood that remains after clotting has occurred, which means it lacks clotting factors like fibrinogen.$\newline$ - Therefore, serum is actually blood minus cells and clotting factors, not blood plus fibrinogen.$\newline$ - Hence, Option 2 is incorrect.$\newline \bullet$Option 3: Lymph = Plasma + RBC + WBC$\newline$ - Lymph is a fluid similar to plasma but contains fewer proteins and no RBCs.$\newline$ - It primarily consists of WBCs, especially lymphocytes, and is part of the lymphatic system.$\newline$ - Therefore, Option 3 is incorrect.$\newline \bullet$Option 4: Blood = Plasma + RBC + WBC + Platelets$\newline$ - Blood is indeed composed of plasma, RBCs, WBCs, and platelets.$\newline$ - This is the correct composition of blood.$\newline$ - Therefore, Option 4 is correct.$\newline$Thus, the correct option is Option 4.