Which of the following is an insulator? A. Mercury B. Carbon C. Germanium D. Glass

The correct answer is: D. Glass

An insulator is a material that

does not allow electricity to flow through it. Glass is a good insulator because it is made up of tiny particles called atoms that are held together by strong bonds. These bonds prevent the electrons in the atoms from moving freely, which is what allows electricity to flow.

Mercury is a metal, and metals are good conductors of electricity. Carbon is a non-metal, and non-metals are generally poor conductors of electricity. Germanium is a semiconductor, which means that it can conduct electricity under certain conditions.

In conclusion, glass is the best insulator among the given options.