The correct answer is: C. East and West Champaran.
The Triveni canal is a canal in Bihar, India. It is a branch canal of the Gandak canal, and it irrigates the districts of East Champaran and West Champaran. The canal was built in the early 1900s, and it is one of the most important irrigation canals in Bihar.
The Triveni canal is about 100 kilometers long, and it has a discharge capacity of about 100 cubic meters per second. The canal irrigates about 100,000 hectares of land, and it is used to grow a variety of crops, including rice, wheat, sugarcane, and vegetables.
The Triveni canal is an important source of irrigation for the districts of East Champaran and West Champaran. It helps to improve the agricultural productivity of the region, and it also provides employment for a large number of people.
The other options are incorrect because they do not irrigate the districts of East Champaran and West Champaran. Option A is incorrect because it irrigates the district of East Champaran. Option B is incorrect because it irrigates the district of West Champaran. Option D is incorrect because it irrigates the district of Muzaffarpur.