Earliest system to be function in fetus is ?

Ans. is 'c' i.e., Circulatory Fetal period extends from the beginning of 3rd month to the end of intrauterine life (till bih). It is the period of maturation of tissues and organ and rapid growth of body occurs. By the end of organogenesis (end of embryonic period) most of the organ systems are developed, however, the function of most of them is negligible except cardiovascular system (cardiovascular system is first to function).