Body Fluids and Circulation

Coagulation needs the clotting factors, the most important being fibrinogen, which is converted into insoluble fibrin threads.
Blood serum is plasma without the clotting factors: it is the pale yellow fluid left after the blood has clotted.
Since serum has no fibrinogen and other clotting materials, it cannot take part in clotting and will not coagulate.
Blood plasma contains fibrinogen, so it coagulates.
Whole blood from the pulmonary vein contains all the clotting factors and platelets, so it coagulates.
Lymph from the thoracic duct also contains fibrinogen and can clot, though slowly.
So the drop that will not coagulate is blood serum.

The major proteins of blood plasma are fibrinogen, globulins and albumins.
Globulins are primarily involved in the defence mechanisms of the body.
Antibodies are immunoglobulins; they belong to the $\gamma$-globulin (gamma globulin) fraction of the serum globulins, while the $\alpha$ and $\beta$ globulins transport hormones and other substances.
So a major deficiency of antibodies will show up as a low level of serum globulins, which is the confirmatory evidence.
Fibrinogen is needed for the clotting or coagulation of blood.
Albumins help in maintaining the osmotic balance of the blood.
Haemocytes are blood cells, not the proteins that make up antibodies.

The complete aerobic oxidation of glucose to $CO_2$ and water takes place through the Krebs cycle and the electron transport system, which are located in the mitochondria.
Mature mammalian red blood cells lack a nucleus, mitochondria and other cell organelles; this leaves more room for haemoglobin.
Since they do not have mitochondria, the red blood cells cannot carry out the Krebs cycle.
They obtain their energy only by anaerobic glycolysis, in which glucose is converted to lactic acid, so they respire only anaerobically.
This also ensures that they do not use up the oxygen they carry.
Unstriated muscle cells, liver cells and white blood cells all have mitochondria and can oxidise glucose aerobically.
So the cells that cannot metabolise glucose to carbon dioxide aerobically are the red blood cells.