What is not contained in our blood?
a. blood plasma
b. leukoctyes
c. erythrocytes
d. lymph

The answer is D. lymph

Leukocytes are white blood cells, erythrocytes are red blood cells all contained in the plasma along with other things and collectively referres to as the blood.
Lymph is found in the lymphatic system.

answer: - b cells

explanation: -

there are many types of white blood cells present in our body. one such class of white blood cells are the lymphocytes. the b cells belong to the lymphocyte class of wbcs. the b cells perform their action against the pathogen by producing specialised proteins called as antibodies. these antibodies are produced as and when the b cells encounter pathogens in response to the antigens present on the surface of the pathogen. these antibodies bind to the antigens present on the pathogen and then, target them for destruction by other cells of the immune system.

so, the b cells mediate their action by identifying the antigens present on the surface of the pathogens and then producing antibodies in return to mediate its effect.