d. Start at A. Tell B you need a few weeks to consider. Assuming everything is ok at A for a few weeks, turn down B. Reasoning: Company A hired you after only

d. Start at A. Tell B you need a few weeks to consider. Assuming everything is ok at A for a few weeks, turn down B. Reasoning: Company A hired you after only a 40 minute phone interview. Wait to make sure you indeed can start that job, that you get paychecks, and that there are no surprises.