Based on the context of each excerpt from N. Scott Momaday's The Way to Rainy Mountain, choose the word that most closely matches the meaning of the bolded word.

radioactive dating, also known as  radioisotope dating  is a process that in  estimating the approximate  age  of  rocks. these data can be analyzed from  the studies dealing with the  decay of the radioactive elements that are present in these rocks. in nature, there are a few types of materials or atoms which are quite unstable and they spontaneously decay or breakdown to form other kinds of atoms.

25. twelve tables

26. having important positions chosen by lot

a big one is

to appoint and regulate officers of the land and naval forces,

which caused much controversy ending the articles