If a scientist knows the relative age of a fossil, he can also know
the relative age of the rock where it was found.
how long the organism was alive.
how it became extinct.
the type of climate from which it came.

The correct answer is the relative age of the rock where it was found.

Explanation:

Any preserved impression, remains, or trace of any once-living thing from past is known as a fossil. The examples comprise shells, bones, stone imprints of microbes or animals, exoskeletons, and the objects preserved in hair, oil, amber, petrified wood, DNA remnants, and coal. The whole of fossils is considered as the fossil record.  

By knowing the relative age of the fossil, one can also know about the relative age of the rock surrounding it. It is due to the fact that when something died and got fossilized, it had rock formed around it and the rock is of a similar basic age as of the fossil.