A train on a straight track goes in the positive direction for 5.9 km, then backs up for 3.8 km. What is the distance covered by the train?

When can a theory be modified if a new type of technology allows for new observations that raise new questions? a-immediately, while the questions about the theory are being asked b-after new hypotheses related to the theory are tested in experiments c-only after the new observations disprove all parts of the theory d-while scientists begin to think about how the theory could improve