Thanks for the question! We're looking for a commonality between the three theoretical approaches to the LHB that the passage presents us. The first theoretical approach starts on line 18, and tells us that an asteroid or comet orbiting the sun disintegrated and bombarded the earth (lines 20-21). The second theoretical approach discusses continuous, declining heavy bombardment throughout the inner solar system (lines 27-28). The third group believes that there was a relatively sharp, brief cataclysmic cratering period from a body within the Earth-Moon system (lines 31-38). In all three groups, the LHB happened, and then cratering decreased significantly as whatever event each theory claims to have happened ended, which allows life on earth to exist. This is what (C) tells us. Hope this helps!
