Final answer:
Long strings of monomers that have been combined are called polymers, which are formed through polymerization and are a crucial component in both synthetic and biological contexts.
Step-by-step explanation:
Long strings of monomers that have been put together are known as polymers. Polymers are formed through a process called polymerization, where monomers, the individual units, are linked together by covalent bonds to form these large molecules. In biology and chemistry, these polymers are essential, and they include important substances such as proteins, starch, cellulose, and DNA, often referred to as macromolecules due to their large size.
Therefore, the correct answer to the question - Long strings of monomers which have been put together are: A) Polymers.