(A) True. Spontaneous abortions,also known as miscarriages,can occur due to various biological factors.
$(b)$ False. Infertility is the inability of a couple to produce children in spite of unprotected sexual cohabitation. It can be due to abnormalities in either the male,the female,or both partners.
$(c)$ False. While lactational amenorrhea is a natural method of contraception,it is only effective for a period of up to six months following parturition,provided the mother is exclusively breastfeeding.
$(d)$ True. Providing sex education and creating awareness about reproductive health,STIs,and contraception are essential strategies for improving the reproductive health of a population.