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: Complex chemistry is needed to carry out all the functions of life. 
Sentence2: Chemistry is primarily concerned with matter, energy, and their interactions.

SOLUTION: chemistry

PROBLEM: Sentence1: Gravity is a force that pulls on things. 
Sentence2: A force that pulls on things pulls objects towards planets.

SOLUTION: force

PROBLEM: Sentence1: Almost all fossils are found in water-laid sediments. 
Sentence2: Fossils of a water animal or plant are located in water-laid sediments.

SOLUTION:
sediments