How is radioactive decay used to date sedimentary rocks? a. the amounts of potassium and argon in sedimentary rocks are measured. b. the amounts of carbon-14 and nitrogen in sedimentary rocks are measured. c. the amounts of unstable elements in each layer of the sedimentary rocks are compared. d. the amounts of unstable elements in the volcanic layers above and below the sedimentary layers are measured

The answer is; B

Different radioactive isotopes have different half-lives (which is the amount of time taken for half of the total isotopes in the material to decay). Therefore, to predict the age of a rock in radiometric dating, the initial amount of the isotopes is determined and then that of decayed ones is determined. The predictability of the half-lives of the elements is then used to determine the age of the rock/fossil.  

answer; the tunica intima also called tunica interna, consists of elastic fibers,connective tissue and smooth muscle cells;