Final answer:
The best course of action would be to respect their decision and wait for their call.
Step-by-step explanation:
In this situation, the best course of action would be to respect their decision and wait for their call (option a).
When the spokesperson indicates that they need to talk it over and will call you within 48 hours, it means that they are considering your offer and need time to discuss it internally. Pushing for an immediate commitment (option c) or insisting on a decision before leaving the meeting (option d) may come across as pushy and could potentially harm your relationship with the potential client.
Offering a time-limited discount (option b) may seem desperate and could devalue your product or service.