Which one of the following statement is correct with regards to the material of electrical insulators?

CONCEPT:

• Insulators: The substances through which electric charges cannot flow easily are called insulators.
• In the atoms of such substances, electrons of the outer shell are tightly bound to the nucleus.
• Due to the absence of free charge carriers, these substances offer high resistance to the flow of electricity through them.
• Most of the non-metals like glass, diamond, porcelain, plastic, nylon, wood, mica, etc. are insulators. 

EXPLANATION:

• Insulators possess high resistivity and low conductivity.
• Their atoms have tightly bound electrons that do not move throughout the material.
• Because the electrons are static and not freely roaming, a current cannot easily pass.

• An important difference between conductors and insulators is that when some charge is transferred to a conductor, it readily gets distributed over its entire surface.
• On the other hand, if some charge is put on an insulator, it stays at the same place.