Final answer:
Carbon finds its way into rock primarily through the formation of sedimentary rocks, where it can be stored for millions of years. While groundwater and decaying plant matter also contribute to this process, sedimentary rock formation is the most direct method.
Step-by-step explanation:
Carbon can find its way into rock via several processes, but when considering the options provided: decaying plant matter, the formation of sedimentary rocks, groundwater, and carbon dioxide carrying precipitation, the most direct method by which carbon is incorporated into rocks is through the formation of sedimentary rocks. Sedimentary rocks are a major reservoir of stored carbon, and they can store carbon for millions of years. Carbon enters these rocks through processes such as the deposition and solidification of mineral carbonates from the ocean water or the accumulation of organic material that turns into fossil fuels. Groundwater, which often contains dissolved carbon dioxide, can slowly dissolve carbon in rocks and carry it to the ocean, making it another way for carbon to be transported into rock formations.
Thus, the correct answer to the question, 'Carbon can find its way into rock via:' is b. the formation of sedimentary rocks, although in a broader sense, all the options listed are parts of the complex carbon cycle where carbon is moved and stored in different forms.