Sedimentary rocks are turned into metamorphic rocks by . A. chemical changes and heating-cooling cycles
B. calcification of minerals over long periods of time
C. the expansion of crystals when inside magma flows
D. extreme temperatures and pressures

There is no reason to think the results are biased or not conducted properly but you should not assume the results are correct just because they were done in a laboratory so the answer would be c. it is likely to be reliable because the results support the conclusion presented.

What are the options? physical property can be color, smell, opacity, viscosity, density, infra red spectrum, melting and boiling points, attraction and repulson to magnets, etc.