1. The answer is B. They are the building blocks of matter.
Elements are the building blocks of matters. They were also known as chemical elements that composed of atoms and protons. Elements can be seen in the periodic table of elements. Elements were usually combined to create a new chemical compound.
Element has an atomic number, isotopes, isotopes mass and atomic mass, melting point and boiling points, densities, properties, structures, occurrence and origin.
Example of elements:
=> Hydrogen = H
=> Lithium = Li.