What is the name of the test used to determine the relative refractive index between two materials?
A) Griess test
B) Becke line test
C) medullary index
D) gas chromatography

Sorry i don’t know what to do

Year  1936,  lehman predicted that the earths 'inner core' is solid. she observed that the seismic signals during her study were bent and did not pass through instead bouncing back. later it was confirmed that the earth's inner core was solid made up of nickel-iron and had a molten outer core.