Hermann Staudinger studied natural rubber and cellulose and proposed that the polymeric structure of natural rubber is made of repeating units of isoprene, CH2=CCH=CH2. This understanding paved the way to producing many synthetic polymers such as polyethylene (PE) and polypropylene (PP). The properties of these and other common plastics depend on what monomers are used. Additionally, plastics can formed into adhesives, films, and many other shapes. Which is not a reason these plastics are so commonly used today? A) Long-term durability. B) Ease of manufacturing. C) Low temperature synthesis. D) Ability to tailor the end product