During Hadean time, the solar system was forming within a cloud of dust and gas known as the solar nebula, which eventually spawned asteroids, comets, moons and planets. Astrogeophysicists theorize that about 4.52 billion years ago the proto-Earth collided with a Mars-size planetoid named Theia.
A net population decline resulting from an "excess of deaths over births".
Option: A
<u>Explanation</u>:
Demographic transition is a shift from higher to lower level of fertility and mortality.Rapid development in industrialization and urbanization in 
century resulted into enormous population growth. But decline in early 
century covered many reasons like consequences of two calamitous wars, where Europe suffered large population declination due to battle death and civilian causalities in World War I and II. Hence the acceleration of population growth in 19th century but downfall in 20th is also considered as balance.
There are many ways to measure distance between Perth and Ireland.
First of all, you should know what kind of distance you want to measure: absolute or relative? this means wither it is in a straight line (which might not be suitable for actually doing it in terms of traveling), or relative, and you would be considering possible routes (boat, plane..).
Secondly, you must choose the point in Ireland.
You can use some online tools that help you with measuring distances. An example is:
https://www.freemaptools.com/how-far-is-it-between-Belfast_Northern-Ireland-and-Perth_Australia.htm
You can then change the cities.
Hope this helps.
d is the correct answer I belive. hope this helped>>
