Final answer:
In the context of the question, (3) 'cognizant' is the synonym of 'sentient' that suggests awareness or consciousness, making it the best choice among the options.
Step-by-step explanation:
The synonym of 'sentient' that best fits in the context of the given question is cognizant. Being sentient means having the capacity to perceive or feel things. Therefore, when talking about someone in a coma, whether they are sentient is questioning their ability to be aware of and respond to the environment around them.
'Sentient' is most synonymous with 'cognizant' because it implies having knowledge of or being aware of something, which requires some level of consciousness or perception. While 'alert' and 'alive' are related concepts, 'alert' might suggest a higher level of responsiveness and 'alive' indicates that the person is not dead but does not necessarily imply awareness.