Explanation:
1. Height Relatives to reference point, Mass, and strength of the gravitational field it's in
2. Distance in the magnetic field
mass number is defined as sum of number of protons and neutrons
so here for Isotope A
Isotope A contains 56 protons and 80 neutrons.
Mass number will be given as

For Isotope B
Isotope B contains 55 protons and 81 neutrons.

For Isotope C
Isotope C contains 57 protons and 80 neutrons.

For Isotope D
Isotope D contains 56 protons and 74 neutrons.

<em>So here Isotope A and Isotope B has same mass number</em>
Answer: 
Explanation:
Given
Volume of air 
Temperature of air 
Increase in temperature 
Specific heat for diatomic gas is 
Energy required to increase the temperature is
![\Rightarrow Q=nC_pdT\\\\\Rightarrow Q=n\times \dfrac{7R}{2}\times \Delta T\\\\\Rightarrow Q=\dfrac{7}{2}nR\Delta T\\\\\Rightarrow Q=\dfrac{7}{2}\times \dfrac{PV}{T}\times \Delta T\quad [\text{using PV=nRT}]](https://tex.z-dn.net/?f=%5CRightarrow%20Q%3DnC_pdT%5C%5C%5C%5C%5CRightarrow%20Q%3Dn%5Ctimes%20%5Cdfrac%7B7R%7D%7B2%7D%5Ctimes%20%5CDelta%20T%5C%5C%5C%5C%5CRightarrow%20Q%3D%5Cdfrac%7B7%7D%7B2%7DnR%5CDelta%20T%5C%5C%5C%5C%5CRightarrow%20Q%3D%5Cdfrac%7B7%7D%7B2%7D%5Ctimes%20%5Cdfrac%7BPV%7D%7BT%7D%5Ctimes%20%5CDelta%20T%5Cquad%20%5B%5Ctext%7Busing%20PV%3DnRT%7D%5D)
Insert the values

Answer:
Mass is the measure of an object's matter (what it's made up of). The greater an object's mass, the greater its gravitational force. The earth has a strong attracting force for objects with smaller mass (including the moon), and the sun has an attracting force on the earth and other planets in our solar system.
Cereals are usually fortified with three most common minerals and vitamins which are:
1- Iron
2- Vitamin D
3- Vitamin B-12
Comparing the above to the given choices, we will find that the best answer is:
b. iron