The correct answer is A. An electron that has been freed from its parent atom.
A free electron is an electron that is not bound to an atomic nucleus. It can exist in a vacuum or in a material, such as a metal. Free electrons are important in many areas of physics and chemistry, including electricity, magnetism, and semiconductors.
Option B is incorrect because a free electron does not cost anything. It is a fundamental particle that is not created or destroyed.
Option C is incorrect because a free electron has a negative electrical charge.
Option D is incorrect because a free electron has the same amount of charge as a normal electron.
Option E
is incorrect because there is no such thing as a free electron that has twice the amount of charge of a normal electron.