Concept:Blocks of the periodic table are named after the outermost subshell being filled with electrons.Explanation:The lanthanides fill the 4f subshell.The actinides fill the 5f subshell.Elements that fill f orbitals are grouped together in the f-block.This block is usually placed as a separate row at the bottom of the periodic table.These elements are also called inner transition metals.They do not belong to the s-block, p-block, or d-block.Answer:C. f-block