An ion is:
a. part of the vacuum tube
b. a measurement in rad's
c. a negative force
d. an atom that has lost an electron

The correct answer is D. An ion is an atom that has lost an electron.

Explanation:

An ion is an electrically charged particle consisting of an atom or molecule that is not electrically neutral. Conceptually this can be understood as that, from a neutral state of an atom or molecule, electrons have been gained or lost; This phenomenon is known as ionization.

When an atom loses or gains electrons, the species formed is an ion and carries a net electric charge. Since the electron has a negative charge, when one or more electrons are added to an electrically neutral atom, a negatively charged ion is formed. Losing electrons produces a positively charged ion. The number of protons does not change when an atom becomes an ion.

none

explanation:

you did not provide anything to go off of.

answer: the answer is d.

explanation: this is because when you exercise you make your muscle produce a certain liquid, that does not evaporate it.   also when you exercise you do not reduce muscle fiber.   and it does not really control your twitch that much.