I believe that your answer is true
As much as 90% of the matter in the universe my be unseen i.e. dark matter. There is a variety of explanations offered by many astronomers and physicists for this dark matter. It could merely be ordinary material such as ultra-faint stars, cold gas, large or small black holes or dust scattered around the universe, all of which emit or reflect too little radiation for our instruments to detect. It could also consist of exotic, unfamiliar particles that we have not figured out how to observe.
The question is incomplete. The complete question is :
If the entire population of Earth were transferred to the Moon, how far would the center of mass of the Earth-Moon population system move? Assume the population is 7 billion, the average human has a mass of 65 kg, and that the population is evenly distributed over both the Earth and the Moon. The mass of the Earth is 5.97×1024 kg and that of the Moon is 7.34×1022 kg. The radius of the Moon’s orbit is about 3.84×105 m.
Solution :
Given :
Mass of earth, 
Mass of moon, 
Mass of each human, 
Therefore mass of total population, 

Let the earth is at the origin of the coordinate system. Then,
Since 

Hence if we shift all the population on the moon there will be negligible change in the mass of the moon and earth. Hence there will not be any significant shift on the centre of mass. i.e.


from the earth.
ITS C
This element tends to lose 2 electrons to become a 2+ ion, is the correct statement regarding the element calcium. Calcium has 2 electrons in its outer shell and it is easier to lose them than it is to gain enough to become stable. When stable it has 2 more protons than electrons forming a 2+ ion.