the rule for controls is that

a. controls are only necessary if you're not doing an experiment

b. everything should remain the same between experimental groups

c. there should be only one independent variable and one dependent variable

d. the only change we make between experimental groups is to the independent variable

Hormones are chemical molecules produced by endocrine glands. one such endocrine gland is the thyroid gland, which synthesizes the thyroid hormone, which in turn affects the heart muscles. which two statements describe the probable reason for the function of the hormone? the cells in the heart have specific receptors that allow for the intake of hormones. the heart and the endocrine glands have the exact same types of cells. all cells make the same types of hormones. thyroid hormones show their effect on the heart by means of specialized cells. thyroid cells and cardiac cells have different dna.