What have scientists observed in order to learn about earths interior?

You can tell from this karyotype that the individual is female because the karyotype has two chromosomes labeled

The large increase in atmospheric carbon dioxide in the last 50 years most likely comes from a. an increase in cellular respiration b. increased decomposition by bacteria c. an increase in the burning of fossil fuels d. an increase in photosynthesis

How are fossils most commonly formed