Answer:
The correct option is evidence of life coming to earth
Step-by-step explanation:
Astrobiology is an intra-disciplinary field in science that deals with the study of life outside of the earth-world and seeks to determine how this life can be detected. From this definition, it can be deduced that astrobiologists are concerned with finding evidence of life coming to earth.
NOTE: The last option looks tricky but some of what astrobiologists are concerned about are life within the solar system but outside of earth, hence the last option is not the answer.