The correct option is
D I: Big bang, II: 20 billion
The universe we see today, an old, vast and empty space composed of galaxies, is almost 20 billion years old.
The Big Bang theory attempts to explain how the universe began with a giant blast (huge explosion) of energy which could not be explained in physical terms, completely unimaginable. It is the most accepted theory to explain the origin of the universe.
With time, the universe expanded and temperature went down. Hydrogen and helium gases were formed.
On the other hand, the theory of spontaneous generation and panspermia explain the origin of life on earth after its formation.
The theory of spontaneous generation was strongly supported by Von Helmont. This theory states that life originated from the non-living matter spontaneously.
Panspermia theory states that life came from the outer space. It is believed that units of life called spores were transferred to earth by asteroids or meteors from space which germinated to give rise to life on earth.
So, the correct answer is option 'd'.