Theory:

     He was also put on the chain on Sundays when his mistress went to spend the afternoon with her married sister who lived in a solitary house on the other side of the mountain-lake, a good hour’s walk through the dense forest. It was not supposed to be good for him to wander about in the forest with all its temptations; it was better to be on the safe side. He was also a bad sailor and had once taken such a fright at a sudden gust of wind that he had upset the boat and he and his mistress had to swim to the shore. Now he knew quite well what it meant when his mistress put him on the chain on Sundays, with a friendly tap on his head and the promise of an apple on her return if he had been good during her absence. He was sorry but resigned, like a good dog, when his mistress tells him he cannot come with her for a walk.
Explanation:
 
The bear did not like to be chained, and therefore got irritated when he was on chains. But during the daytime, he was never on chains, if he behaved. This was because he was a friendly bear and that he could never bring harm on anyone. But he was put on chains during the night time and also on Sundays. It was on Sundays that his mistress was absent. She visited her sister, who was married. Her sister lived on the other side of the mountain lake, across the dense forest. It took around an hour to reach her house. The lady spent all Sunday afternoons with her sister.
 
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Solitary house on the side of a lake
 
The lady did not consider it safe for the bear to travel through the forest. This was because she thought that he might be tempted to go back to his roots. In the wild, he is more prone to temptations. There is a possibility for him to see other wild animals or bears and get influenced by their actions. He might question as to why he is different from the rest of his pack. He eats apples, is controlled by people, is chained during nights whereas the bears in the wild are free, roam around the forest and eat what they find. This might impact the bear and he may feel like going to the wild. The bear had a bad experience with the travel, as he was scared of a sudden wind that blew across their boat and his sudden movement had upset it. He had to swim across the river with his mistress. This was also a reason to avoid taking him during the trips.
 
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Bear in a boat
 
The bear has got used to the chaining after a few days, as every animal gets adapted to the existing conditions after a few days. He understands that the chaining is temporary and that he will soon be relieved from it. The mistress gives him gifts to pacify. He understands that she might give him an apple and a pat on his back if he is well behaved when she returns. He is tamed to the extent that a pat on his back makes him happy and accepting of the chain. He has totally come away from his aggressive roots and has taken the submissive role in the house. Although he is worried about the fact that he cannot follow her, the results make him agree to not accompanying her during the trip. He behaves like a loyal dog who is ready to please his master.
 
Meanings of difficult words from the paragraph:
 
S.No
Words
Meaning
1
SolitaryAlone
2
DenseThick
3
SailorA person who travels by boat or ship
4
Gust of windA sudden sharp increase in the speed of wind
5
ResignedTurn back
6
InfluencedTo have an effect on or power over somebody
7
PacifyTo make somebody who is angry or upset be calm or quiet
8
SubmissiveAllowing yourself to be controlled
9
AccompanyingTo go with/follow someone
Reference:
National Council of Educational Research and Training (2006). Supplementary. The Bear Story (pp.52-57). Published at the Publication Division by the Secretary, National Council of Educational Research and Training, Sri Aurobindo Marg, New Delhi.