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: Acid rain is precipitation which pH is 5.7 or lower. 
Sentence2: gases from burning coal causes precipitation which pH is 5.7 or lower.

SOLUTION: 5

PROBLEM: Sentence1: mountains are formed by earthquakes. 
Sentence2: Mountains are formed by moving plates.

SOLUTION: are

PROBLEM: Sentence1: Hermit crabs use the shells of dead snails for homes. 
Sentence2: For example, home and house mean the same thing, but are different search terms.

SOLUTION:
homes