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>
The number converted is 
Explanation:
In order to convert from the original units to the final units, we have to keep in mind the following conversion factors:



The original unit that we have is

Therefore, it can be rewritten as:

Therefore, since the initial number was 0.779, the final value is

#LearnwithBrainly
Answer: 77 degrees
Explanation:
According to the Law of Reflection, when a ray of light strikes a surface, the angle of this ray (incident ray) with respect to the normal of the surface is equal to the angle that forms the reflected ray with the same normal of the surface.
In other words:
Both the incident ray and the reflected ray and the normal to the surface are in the same plane, in addition, the angle of the incident ray is equal to the angle of the reflected ray.
In this context, if the angle of incidence is 77 degrees, the angle of reflection is 77 degrees, as well.
Answer:
infinity
Explanation:
Given that
Resistance = R
Resistivity = ρ
Length = L
Diameter = d
The resistance of wire R given as

A=Area

Now by putting the value of A


When d tends to infinity then d² will also tends to infinity.
So when d tends to zero then the resistance tends to infinity.
Therefore answer is ---
infinity