The correct answer is: C. Either I or II is implicit.
The statement “There is no reason to rule out the possibility of life on Mars” does not imply that there is life on Mars. It simply means that we cannot say for certain that there is no life on Mars. This leaves open the possibility that there is life on Mars, and therefore that we should explore the planet to find out.
The statement does not imply that the search for life is the only reason for space exploration. There are many other reasons to explore space, such as learning more about our solar system and the universe, developing new technologies, and inspiring people to pursue careers in science and engineering.
Therefore, either assumption I or assumption II is implicit in the statement.