This question tests the understanding of the differences between a personal search agent and a job board. The correct answer is B because job board websites usually require users to search for new job postings manually, whereas personal search agents automate this process. Option A is incorrect because both can provide real-time updates. Option C is false as personal search agents are not limited to entry-level jobs. Option D is incorrect because it describes a potential feature of job board websites but is not the main difference.