Mathematically define heat capacity with equations.

   The amount of energy needed to heat the body by 1 ° C (Q)

Explanation:  The heat capacity or as it is called the thermal mass is the amount of energy needed to heat the body by 1 ° C. When the body is said, it refers to any object in any aggregate state. The energy required for the body to warm up by 1 ° C is expressed in joules, and is obtained when the specific heat of the body multiplies with the body mass and with the change of temperature:

Q = m·c·ΔT

Q - heat capacity (J),

m - mass of the body (g),

c - specific heat of the body (J/g-°C),

ΔT - change in temperature (°C)

the correct option is c.

isotopes refers to different forms of the same element with the same atomic number but different mass number as a result of difference in their neutron numbers. isotopes have different relative atomic mass but share the same chemical properties.