A substance that enters into a chemical reaction is called a(n) . catalyst
enzyme
product
reactant

The substances that go into a chemical reaction are called the reactants, and the substances produced at the end of the reaction are known as the products.

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Explanation:

answer; /// i believe that the correct answer is ( monophasic ); ethinyl estradiol- ethynodiol diacetate is a monophasic oral contraceptive agent; ///

"menstrual cycle is a complex cycle that consists of several processes. order of occurrence of steps in menstrual cycle are as follows:

1. high progesterone levels maintain the endometrium lining of the uterus.

2. endometrium lining breaks down and low levels of estrogen stimulate the pituitary to release fsh and lh.

3. fsh and lh stimulates the follicles to develop and the oocyte to produce estrogen.

4. rising estrogen levels suppress fsh production and development of other follicles.

5. a spike in lh causes follicle to rupture.

6. a breakdown of corpus luteum causes progesterone level to drop."