The solid linear cytoskeletal elements having a diameter of 6 nm and made up of a single type of monomer are known as Intermediate filaments, Microtubules, Lamins, or Microfilaments?

The cytoskeleton is unique to eukaryotic cells. It is a dynamic three-dimensional structure that fills the cytoplasm. This structure acts as both muscle and skeleton, for movement and stability. The long fibers of the cytoskeleton are polymers of subunits. The primary types of fibers comprising the cytoskeleton are microfilaments, microtubules, and intermediate filaments. Microfilaments are fine, thread-like protein fibers, 3-6 nm in diameter. They are composed predominantly of a contractile protein called actin. Microtubules are cylindrical tubes, 20-25 nm in diameter. They are composed of subunits of the protein tubulin—these subunits are termed alpha and beta. Intermediate filaments are about 10 nm diameter and provide tensile strength for the cell. Lamin is the protein present in intermediary filaments. So, the correct answer is 'Microfilaments'.