Answer:
1. Where he describes his people's history.
2. When he tells the Story his Grandmother told him.
Explanation:
1. When describing the history of his people and the land they settled on, N. Scott Momaday in The Way to Rainy Mountain uses longer sentences to properly showcase the landscape and history of his people. For example, in the text we see this description;
"When the Kiowas came to the land of the Crows, they could see the dark lees of the hills at dawn across the Bighorn River, the profusion of light on the grain shelves, the oldest deity ranging after the solstices. Not yet would they veer southward to the caldron of the land that lay below they must wean their blood from the northern winter and hold the mountains a while longer in their view."
Notice how the long sentences, filled with multiple phrases and clauses help paint a picture of the landscape.
2. When he tells the story that his grandmother told him about the legend the Kiowas made at the base of the rock, he starts to use shorter sentences. This is probably because that was how she told her stories, in short sentences.
Notice the short sentences in the story are from this extract;
"Eight children were there at play, seven sisters and their brother. Suddenly the boy was struck dumb, he trembled and began to run upon his hands and feet. His fingers became claws, and his body was covered with fur. Directly there was a bear where the boy had been..."
