Which of the following can be a disadvantage of search agents

A．Personal search agents are indispensable to job hunters.
B．Some sites keep E-mailing job seekers to trace their demands.
C．Personal search agents are also helpful to those already employed.
D．Some agents stop sending information to people once they are employed.

A．By searching openings in a job database.
B．By posting a matching position in a database.
C．By using a special service of a database.
D．By E-mailing his resume to a database.