A scientist is trying to develop a more efficient way to recycle paper this type of chemistry is known as

Green chemistry

Explanation:

Green chemistry is the design of chemical products and processes that reduce or eliminate the use or generation of hazardous substances. Green chemistry applies across the life cycle of a chemical product, including its design, manufacture, use, and ultimate disposal(EPA, 2017).

Green chemistry, also called sustainable chemistry, is an area of chemistry and chemical engineering focused on the design of products and processes that minimize or eliminate the use and generation of hazardous substances(wikipedia).

Thus, any research in chemistry geared towards waste reduction(such as  more efficient methods of paper recycling) and recycling of other materials as well as placing less demands on the natural sources of materials is known as green chemistry or sustainable chemistry.

i'm assuming that the correct answer is indeed the first one/ "a"..