The maintenance of Mullaperiyar Dam has always been an

Solution

The word ‘adjoining’ is correct here. It means ‘near, next to, or touching.’ Penchant- a liking for, an enjoyment of, or a habit of doing something, especially something that other people might not like. Harbinger- a person or thing that shows that something is going to happen soon. Preponderance- the largest part or greatest amount. The maintenance of Mullaperiyar Dam has always been an issue between two adjoining States in India- Kerala and Tamil Nadu.