Question

Within the first second after the Big Bang the universe was filled with high-energy, gamma-ray photons. These photons created huge numbers of elementary particles and their antiparticles through pair production. What happened to these particles? They are still here. They combined to create the first atoms and molecules that compose the physical universe. The particles are still with us as atoms and molecules, but almost all of the antiparticles disappeared. These particle-antiparticle pairs annihilated to produce more photons. This pair production was followed by the era of cosmic inflation during which these particles spread out to produce the matter densities that we see today.

Answer 1

The Big Bang should have created equal amounts of matter and antimatter in the early universe. But today, everything we see from the smallest life forms on Earth to the largest stellar objects is made almost
entirely of matter. Comparatively, there is not much antimatter to be found. Something must have happened to tip the balance. One of the greatest challenges in physics is to figure out what happened to the
antimatter, or why we see an asymmetry between matter and antimatter.

Antimatter particles share the same mass as their matter counterparts, but qualities such as electric charge are opposite. The positively charged positron, for example, is the antiparticle to the negatively
charged electron. Matter and antimatter particles are always produced as a pair and, if they come in contact, annihilate one another, leaving behind pure energy. During the first fractions of a second of the
Big Bang, the hot and dense universe was buzzing with particle-antiparticle pairs popping in and out of existence. If matter and antimatter are created and destroyed together, it seems the universe should
contain nothing but leftover energy.

Nevertheless, a tiny portion of matter – about one particle per billion – managed to survive. This is what we see today. In the past few decades, particle-physics experiments have shown that the laws of nature
do not apply equally to matter and antimatter. Physicists are keen to discover the reasons why. Researchers have observed spontaneous transformations between particles and their antiparticles, occurring millions
of times per second before they decay. Some unknown entity intervening in this process in the early universe could have caused these "oscillating" particles to decay as matter more often than they decayed as
antimatter.

Hence, most of the antimatter and matter elementary particles annhilated producing more photons, where as one in a billion antimatter particle dissapeared instead of anhillating with another matter counterpart
This assymetry caused the current universe

So option a is incorrect, because not all matter particles are here today, as most of them got anhilated inthe beggining of time
option b is correct
option c is partially correct as some pairs did not interact to produce photons
option d is also correct partially

hence, if this is a single choice question , Option b is correct
If this is a multiple options coorect type question , then Option b, c and d are correct