Which of the following statements is true?

A: The number of electron shells in an atom is called the atomic number.
B: Boiling and melting points are chemical properties.
C: A molecule of oxygen can have atoms of carbon in it.
D: Elements are substances made of only one type of atom.

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the corpus luteum secretes estrogens and progesterone. the latter hormone causes changes in the uterus that make it more suitable for implantation of the fertilized ovum and the nourishment of the embryo. if the egg is not fertilized, the corpus luteum becomes inactive after 10–14 days, and menstruation occurs.

i hope this : )

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