TASK DEFINITION: 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.
PROBLEM: Sentence1: smell is used for finding food by some animals. 
Sentence2: Food includes small rodents and birds.

SOLUTION: food

PROBLEM: Sentence1: Mollusks are invertebrates such as the common snail. 
Sentence2: Another common snail is the decollate snail.

SOLUTION: snail

PROBLEM: Sentence1: An astronaut is a scientist who is a space explorer. 
Sentence2: A scientist who is a space explorer requires preserved food for extended flights.

SOLUTION:
explorer