Which of the following best describes an isotope? select one:
a. an atom that has bonded with another atom to form a molecule.
b. an atom that has gained or lost electrons and has an electrical charge.
c. an atom that has more or fewer neutrons than protons.
d. an atom that has changed into another atom through loss or gain of protons?

The correct answer is Option c.

Explanation:

An isotope is defined as the chemical specie which belongs to the same element but differ in their mass number.

Atomic number is defined as the number of protons that are present in a neutral atom.

Mass number is defined as the sum of number of protons and number of neutrons present in an atom.

An isotope of same element has same number of protons but they differ in number of neutrons.

For Example:  Isotopes of chlorine are

In isotope:

Number of protons = 17

Number of neutrons = 35 - 17 = 18

In isotope:

Number of protons = 17

Number of neutrons = 37 - 17 = 20

Hence, the correct answer is Option c.

c. because step up transformer steps up the input voltage i.e increases the input voltage  

the number of turns are greater on the secondary side of step up transformer  

transformer does not handle dc current