PDF chapter test TRY NOW

Paheli watched grandmother making mango pickle. After she bottled the pickle, her grandmother poured oil on top of the pickle before closing the lid. Paheli wanted to know why oil was poured? Can you help her understand why?
 
1. Why does Paheli's grandmother pour oil on top of the mango pickle before closing the lid?
 
 2. What is the primary reason for pouring oil on homemade pickles?