Mineral replacement, carbon film and molds are a few examples of a. fossil formation b. fossil index c. fossil preservation d. ancient enviorments ! i'll give

The answer is C i.e. fossil preservation.

Explanation:

Mineral replacement: Dead plants and animals in the water bodies are buried in mud. With time soft tissue decays and hard bones are left. On top of this sediments build up, when the bone enclosed inside the sediment decays, it gets replaced by the minerals.

Carbon films: carbon films appear as imprints on the rocks of specimens such as leaves.

Molds: Carbon films are two dimensional imprints whereas molds are three dimensional impressions of organisms. When organism buried in the sediments get decayed leaving a cavity, it gets filled with material making a mold.

50 inches should be the resultant vector