Answer:
Problem recognition
Step-by-step explanation:
Problem recognition is the stage in the consumer decision-making process that helps the customer to recognize the difference between the actual state and the wanting state.
In the given case, Gilbert recognized his actual state in which his mobile's battery has a short life. This actual state of Gilbert led him to his wanting state in which he wants a phone with a longer battery life.
So, Gilbert is in the problem recognition stage of consumer decision making process.