Mary is testing two stain removers to see which one works best to remove grease from a towel. She put the same amount and type of grease on each of 10 towels. She then treated
each towel with the same amount of stain remover. She used each type of stain remover on 5
towels. What is the independent variable in Mary's investigation?
the amount of grease
the number of towels
the type of stain remover
the amount of stain remover

The answer is constant.

Interphaseinterphase

answer: carbon 14 can only be used to determine the age of the organisms that were once living, and igneous rocks are non living.

explanation:

carbon 14 dating is used to determine the age of the sample by estimating the amount of carbon 14 present in the sample and then comparing it with a reference standard.carbon 14 is a isotope of carbon which is radioactive and unstable. carbon 14 is assimilated by all plants and animals throughout their life from carbon dioxide. however, one the organisms die they stop this assimilation and the carbon 14 content starts to decrease.by knowing how much of carbon 14 is left in an organism after his death, one can estimate the age of the organism. the materials whose age can be estimated by carbon 14 method are the organic compounds. however, some inorganic compounds such as aragonite   shell can also be dated.however, if we consider the igneous rocks it is a non living component which never accumulated carbon 14 in it and thus, we cannot use carbon 14 dating method to estimate its age.