Theory:

     That day she played for hours on the grassy slopes of the hills. She met a herd of wild goats who asked her to join their group. But Chandni politely refused. She wanted to enjoy her new freedom all by herself.
 
     The sun disappeared behind the hills, and soon darkness enveloped the grass, the flowers and the trees. The wind stopped blowing, and there was stillness all around except for a strange sound which was coming from the bushes. The sound was like a grunt. What was it? It wasn’t Abbu Khan’s voice calling her back to the compound; nor was it the voice of another goat. Then Chandni thought of the dangerous wolf who lived in the hills. She felt scared.
Explanation:
 
Chandni was overjoyed with the achievement of a long-held dream. She continued to play for hours on end on the limitless expanse of green-grassed hills. She also respectfully refused to join the herd of wild goats who approached her and invited her to join them. She desired to enjoy her freedom on her own. After a while, evening fell, and the hills were shrouded in darkness.
 
A weird sound came from the bushes, and there was silence all around the hills. From the bushes, a grunting voice was heard. Chandni was able to discern one thing: it was neither Abbu Khan's nor any other goat's voice. Chandni then connected to Abbu Khan's tale. Abbu Khan's stories of dead goats and his warnings about the deadly old wolf that resided in the hills came to Chandni's mind. Chandni was terrified.
 
Meaning of difficult words:
 
S.No
Words 
Meaning 
 1.
GruntTo make a short, low sound from the throat
2.
Discern To know or understand something
3.
ResideTo live in a particular place
4.
TerrifiedVery scared or frightened
5.
Politely In a respectful manner
Reference:
 National Council of Educational Research and Training (2007). Chandni – Zakir Husain (pp. 43- 51). Published at the Publication Division by the Secretary, National Council of Educational Research and Training, Sri Aurobindo Marg, New Delhi.