which machine uses the principal of slopes? A . wheelbarrow and crowbar B. pulley and contour road. C. spade and claw hammer D. ladder and staircase

its 42

i say its d?

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explanation:

b r

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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.

sex cells are usually half's then they find another half and make a fertilize egg