The correct answer is: A. CRS
The Chief Railway Safety Officer (CRS) is the head of the Railway Safety Directorate of the Indian Railways. The CRS is responsible for ensuring the safety of all railway operations in India. This includes issuing permits for temporary diversions, which are required when there is a need to close a section of track for maintenance or other reasons.
The Railway Board is the highest executive body of the Indian Railways. It is responsible for the overall management and administration of the railways. However, the Railway Board does not have the authority to issue permits for temporary diversions. This authority is vested in the CRS.
The Chief Engineer (CE) is the head of the engineering department of a railway zone. The CE is responsible for the construction and maintenance of railway infrastructure. However, the CE does not have the authority to issue permits for temporary diversions. This authority is vested in the CRS.
Therefore, the correct answer is: A. CRS