Answer : 3. "किसी वन में, झाड़ियाँ वनस्पति की सबसे निचली परत बनाती हैं।"
Explanation :

All statements about forests are correct

1. In a forest, trees form the uppermost layer of vegetation.

2. Forests protect the soil from erosion.

3. Forests influence climate, water cycle and air quality.