Question

read the text.
not so lonely planet
are we alone? this question has weighed on the minds of humans for centuries. some have long claimed that alien life indeed exists both within earths solar system and beyond. still, conclusive proof of alien life has remained out of reach. recently, however, nasa scientists have given the world a reason to believe that the existence of alien life is not only possible, but probable. recent discoveries suggest that, beyond earth, the solar system is full of conditions that could support life as we know it. continuing evidence of water in other parts of the galaxy, as well as a recent breakthrough discovery of seven habitable exoplanets similar to earth, support the notion that finding alien life is a quickly approaching possibility.
what is the authors main claim or argument?
it is likely that alien life exists beyond earth.
experts have claimed for years that alien life exists.
scientists have discovered evidence of alien life.

Explanation:

The text starts by posing the question of whether we are alone, then mentions that while conclusive proof of alien life has been lacking, recent NASA - related discoveries (conditions supporting life, water evidence, habitable exoplanets) suggest it is likely that alien life exists beyond Earth. This is the main claim. The other options either focus on past claims without the recent evidence - based likelihood or wrongly state that evidence of alien life has been discovered (only conditions suggesting it have been found).

Answer:

It is likely that alien life exists beyond Earth.