Does hydrogen and helium act almost like a furnace in the sun?

Yes

Explanation:

Two isotopes of hydrogen, tritium and protium, undergo nuclear fusion in the sun to give helium, neutrons and a tremendous amount of energy. This reaction occurs at the very high temperature found in the sun and yields tremendous amount of energy.

Given the high temperature at which the said fusion reaction occurs, it is safe to say that hydrogen and helium act as a furnace at the core of the sun.

chert is a sedimentary rock composed of microcrystalline or cryptocrystalline silica. with this little bit of information, you can come to the conclusion that your answer is c.  

explanation:

which

what is a measurement of the earth’s history divided into time periods?

> fossil record <

sedimentary rock

> geologic time scale <

radioactive elements