Fill in the blank Accurate determination of abundances of isotopes became possible with the development of the1)_______. These analyses have shown that some of the oldest rocks on Earth are 4.0 2) ______years old, with some meteorites dating even older than that. 1. A. nuclear fusion reaction B. hadron collider c. mass spectrometer d. Geiger counter 2. A. hundred B. trillion C. thousand D. million e. billion Solution Accurate determination of abundances of isotopes became possible with the development of the c. mass spectrometer. These analyses have shown that some of the oldest rocks on Earth are 4.0 e. billion years old, with some meteorites dating even older than that. .