Final answer:
The main focus of the passage is Jason's absence (b) due to a family emergency, as explicitly stated in the conversation. Despite Jason's unavailability, the project leader remains willing to offer assistance.
Step-by-step explanation:
The conversation reveals that Jason's absence from work and unresponsiveness on the phone are due to a family emergency. The response "He has gone for the day for a family emergency" directly addresses the reason for Jason's unavailability.
The subsequent exchange expresses gratitude for the information and a request for assistance, indicating the willingness of the person in charge of the project to help despite Jason's absence. Therefore, the central information conveyed is Jason's absence for a family emergency, aligning with option (b).