What unique feature of the CISF sets it apart from other CAPFs ?

What unique feature of the CISF sets it apart from other CAPFs ?

It is the only armed force of the Union.
It is the only force to have its own dedicated intelligence wing.
It is the only force whose personnel are deployed to deal with disaster management.
It is the only cost reimbursement force.
This question was previously asked in
UPSC CISF-AC-EXE – 2020
The Central Industrial Security Force (CISF) is unique among the Central Armed Police Forces (CAPFs) in that it is primarily a cost-reimbursement force. While other CAPFs (like BSF, CRPF, ITBP, SSB) are primarily deployed for border guarding or internal security duties with costs covered by the central government, CISF provides security cover to public sector undertakings, industrial units, government buildings, airports, ports, power plants, etc., and the cost of this deployment is reimbursed by the entity receiving the security cover to the government.
The cost-reimbursement model for its deployments is a distinctive feature of the CISF compared to other CAPFs.
Other CAPFs also have armed capabilities (making A incorrect), and while intelligence gathering and disaster management are functions they contribute to (often through deputation to agencies like NDRF or having their own intelligence wings), CISF is not the *only* force performing these roles (making B and C incorrect as unique features).