_____ institution is responsible for management of water resources of Indus River system and for the distribution of water among four provinces of Pakistan.

Correct Answer: A. Indus River System Authority (IRSA)  

The Indus River System Authority (IRSA) is tasked to regulate and monitor the distribution of Indus water resources between provinces, to ensure compliance with the Water Apportionment Accord (WAA), and ultimately to mitigate conflict between provinces.