The castle system helped rulers maintain power in Ancient India by

The caste system helped rulers maintain power in Ancient India by: Giving everyone an opportunity to better themselves through hard work.

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#2 the answer is d

#3 the answer is a

#4 the answer is b

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.