Answer: b. Carry on a conversation
Step-by-step explanation:
There are different levels of intensity when exercising and these require different energy levels and different amounts of air coming into the lungs.
The CDC notes that if you are exercising at a moderate level, the energy and oxygen requirements will not be as high so you can be able to talk to other people without being short of breath from needing more of the oxygen and energy that is being used in the talking.