The most likely place to find fossils are in
a. sedimentary rock.
b. volcanic rock.
c. the sap of ancient trees.
d. beach sand.

The correct answer is A. The most likely place to find fossils are in sedimentary rocks.

Explanation:

Fossils are remains and traces of plants and animals that are preserved in rocks. Although that is often thought, fossils do not have to be 'petrified'. Very many fossils are indeed not petrified. Even from very old rocks fossil remains are known that have hardly changed. Furthermore, many think that fossils are always very old. This is also not justified. Many very young fossils are known, which originated in a period when there were already people on earth.  

The science that studies fossils is called paleontology. This knowledge area helps with research into the succession of rocks, a branch within geology that is called biostratigraphy. As remains of life only fossilize under specific circumstances, the fossil information is limited and by definition incomplete.