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: Coral reefs provide food and shelter to many ocean organisms. 
Sentence2: Coral Reefs Coral reefs are threatened.

SOLUTION: Coral

PROBLEM: Sentence1: Minerals are chemical elements that are essential for body processes. 
Sentence2: minerals are needed by body processes.

SOLUTION: processes

PROBLEM: Sentence1: Evolution causes species to change over time. 
Sentence2: Mutations are required for species to change over time.

SOLUTION:
change