Which of the following is not a flatworm?

1.flukes
2.tapeworm
3.planarian
4.none of the above

mendel's first law states that during the formation of reproductive cells , pairs of hereditary factors for a specific trait separate so that offspring receive one factor from each parent.

explanation:

the level of progesterone is low at the pre-ovulatory phase of the cycle but it gradually increases and the levels are high at the luteal phase. if pregnancy occurs, the level of progesterone will be high throughout the pregnancy.

if egg is fertilized and the mother gets pregnant, progesterone starts preparing the uterus for the implantation. it starts building up the lining of uterus and make it hostile of the period of pregnancy.