What is the name of Katara and Sokka's grandmother?

Katara and Sokka's grandmother is Kanna, commonly called “Gran-Gran.”

Kanna lives with her grandchildren in the Southern Water Tribe after Katara and Sokka's mother, Kya, is killed during a Fire Nation raid. Their father, Hakoda, is away fighting in the war, so Kanna helps care for them before the series begins.

Kanna also connects the Southern and Northern Water Tribes. She was once engaged to Pakku, the Northern Tribe's strict waterbending master, but left him because she rejected the Northern Tribe's restrictions on women learning waterbending as a martial art. Her necklace later allows Pakku to recognize her and changes his attitude toward teaching Katara.

The wrong options are characters from the same family or story: Yue is a Northern Water Tribe princess, Kya is Katara and Sokka's mother, and Hama is an older Southern Tribe waterbender who becomes an antagonist. Kanna is the single canonical answer.