Geography · Indian Rivers and Wildlife

With reference to the Gandak River and the Gharial (Gavialis gangeticus), consider the following statements: I. The Gandak River originates near the Tibet-Nepal border region near Dhaulagiri and is a left-bank tributary of the Ganga, joining it near Hajipur in Bihar. II. The river is known as Kali Gandaki in its upper reaches and as Narayani after its confluence with the Trisuli River in Nepal. III. The Kali Gandaki gorge, formed by this river, is among the deepest river gorges in the world. IV. Within the Ganga river system, the gharial population is now confined exclusively to still-water reservoirs and lakes, having entirely vanished from fast-flowing rivers like the Chambal and Gandak. Which of the statements given above are correct?