Name the method of external recruitment in which business organisations keep a database of unsolicited applicants, make a list of job seekers and fill the vacancies as and when they arise.

The correct option is Casual callers.

Step-by-step Explanation:

External recruitment refers to the process of sourcing and hiring candidates from outside the organization to fill vacant job positions. Among the various methods of external recruitment, Casual Callers is a commonly used approach.

Under this method, business organizations do not actively advertise for a specific vacancy. Instead, many job seekers voluntarily submit their resumes or applications to the organization's office or portal, even when there are no immediate job openings. These are known as unsolicited applicants.

The organization maintains a database or a "waiting list" of these unsolicited applications. When a vacancy arises, the HR department screens this database, identifies suitable candidates, and contacts them to fill the position. This is a cost-effective and time-saving method of recruitment because the organization does not have to spend resources on advertising the vacancy or hosting extensive search campaigns.

Let's briefly understand why the other options are not correct:
1. Direct Recruitment: In this method, a notice is placed on the notice board of the organization specifying the details of the jobs available. Job seekers assemble outside the premises on a specified date, and selection is done on the spot.
2. Employment Exchange: This is run by the government where details of job seekers are registered, and they act as a link between job seekers and employers.
3. Advertisement: This involves publishing job vacancies in newspapers, professional journals, or online portals to attract a wide range of applicants.