Step 1: Read the case carefully.
A software company needs fresh graduates with specialised skills in Artificial Intelligence and Data Analytics. Existing employees lack these skills. A notice was put up in the office asking current employees to introduce any friend or relative who might have the required skills.
Step 2: Determine whether this is an internal or external source of recruitment.
Since existing employees do not have the required skills, the company must look outside the organisation. The candidates being sought (friends or relatives of existing employees) are people from outside the company. So this is an external source of recruitment. This eliminates options (C) Transfer and (D) Promotion, which are internal sources.
Step 3: Differentiate between Direct Recruitment and Recommendation of Employees.
Direct Recruitment means the company places a notice on the enterprise's gate or notice board inviting casual job seekers and walk-in applicants to apply directly without any intermediary. Recommendation of Employees means the company asks its existing employees to recommend friends, relatives, or acquaintances from their personal networks who may be suitable for the open positions.
Step 4: Identify what exactly happened in this case.
The company placed a notice at the reception specifically asking present employees to introduce (recommend) any friend or relative with the required skills. The company is using its existing workforce as a channel to find external candidates. This is not a walk-in style or casual application; it is specifically routed through the existing employees' personal contacts.
Step 5: Match with the correct option.
This method perfectly describes Recommendation of Employees (employee referrals), which is option (B).
Step 6: Conclude.
Using current employees as a bridge to find outside talent through their personal networks is the external recruitment source called Recommendation of Employees.
\[ \boxed{ \text{(B) Recommendation of employees} } \]