This is physical education .,. You notice your cardiovascular endurance is not improving any more when you go for walks. What should you do to continue to improve your cardiovascular endurance?

Slow down and go at a slower pace

Increase the intensity of your exercise

Increase the frequency of your exercise

Decrease the length of time that you exercise

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