State the main function of the following:

(i) Lymphocytes of blood
(ii) Leydig cells
(iii) Guard cells
(iv) Eustachian tube
(v) Corpus luteum

i. Lymphocytes of blood cells -  Antibody production

ii. Leydig cells -  Testosterone hormone production

iii. Guard cells - Helps in opening and closing of stoma

iv. Eustachian tube - Equalises the air pressure on either side of the ear drum.

v. Corpous luteum - Secrets progesterone hormone to prepare uterus to receive the embryo.