Acontraceptive that permanently prevents transport of the sperm or egg to the site of conception is a

The answer is Surgical Contraceptive Methods e.g. Vasectomy(For males) and  Tubectomy(Females).

Vasectomy:- In this method vas deference is cutted and tied so that sperms can't reach uthera.

Tubectomy:- In this method both fallopian tubes are cut and tied, so that no egg can head towards the site of reproduction(Cervix).

Note:- Both process are irreversible.

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.