Immunity is the state of protection against foreign agents. It can be conferred either actively by activating a person 's immune system or passively without activating his own immune system. Following are different examples of how immunity can be attained.
I. Antibodies passed from mother to the child through breast feeding.
II. Treatment of humans bitten by venomous snakes with antivenin, a serum from sheep or horses that have been immunized against the venom.
III. Infection with hepatitis A virus and subsequent recovery from it.
IV. Administration of hepatitis A vaccines. Which of the above are examples of passive immunity ?
(a) I & II only
(b) II & Ill only
(c) I only
(d) I & IV only