Which of the following managerial function leads to optimum use of resources?

Staffing

The correct answer is option 3- staffing.

Staffing helps to ensure optimum utilisation of the human resources. By avoiding overmanning, it prevents under utilisation of personnel and high labour costs. At the same time it avoids disruption of work by indicating in advance the shortages of personnel.
Option 1,2 and 4 are part of staffing process.
There are 5 functions of management- Planning, organising, staffing, directing and controlling.