From the following statements about the menstrual cycle, which two are correct?(i) Lack of menstruation may be indicative of pregnancy.(ii) The changes in the ovary and the uterus are induced by changes In the levels of ovarian hormones only.(iii) LH surge induces ovulation.(iv) If fertilisation occurs, the corpus luteum degenerates immediately.

Lack of menstruation in a normal female may be indicative of pregnancy. During pregnancy, the levels of estrogen and progesterone are high in the blood, which is required for the maintenance of uterus and thus, menstruation does not occur.Rapid increase in LH (called LH surge) induces ovulation. The changes in the ovary and the uterus are induced by changes in the levels of ovarian hormones as well as pituitary hormones. If fertilisation occurs, corpus luteum is not degenerated. Progesterone secreted by it is required for the pregnancy. It is recued by hCG. It only degenerates later at 16th week of pregnancy.