There are no results described in the last sentence. It mentions that certain implications "could be tested," but that's not a description of actual test results.

This is the best answer. The author notes that one aspect of the second theory could be tested in our own solar system. This suggests the second theory might be easier to test than the dark energy theory. Since the author characterizes this relative ease of testing as an "advantage," we have evidence the author considers the ease of testing to be a relevant criterion for evaluating theories.

The last sentence doesn't describe any obstacles to questioning the theory of relativity or other theories in physics. The last sentence merely describes one advantage of the second explanation that might make it easier to test than the dark energy theory.

Although the author mentions that the implications of the second explanation on our understanding of gravity at short distances could be tested, the author doesn't propose an actual experiment for conducting such tests. Merely saying that there could be tests does not constitute a proposal of an experiment.

Although the author mentions that the implications of the second explanation on our understanding of gravity at short distances could be tested, the author doesn't describe the technical requirements of such a test. Merely saying that there could be tests in our own solar system does not constitute a description of the requirements for those tests.