Generate an overlapping word between the given two sentences. When you find the overlapping words, they don't have to match exactly, e.g., "survival" and "survive" are valid overlapping words. Little words like "the" or "of" don't count! You must generate significant words which are not the stop words.
Example: Sentence1: pesticides cause pollution. 
Sentence2: pollution can harm animals.
Example solution: pollution.
Example explanation: The word "pollution" is common to Sentence1 and Sentence2. So, it's a good answer.

Problem: Sentence1: Plants help make oxygen for the air. 
Sentence2: An animal requires plants for survival.

Solution: Plants