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: Polygenic inheritance Polygenic traits are controlled by an unknown number of genes. 
Sentence2: Skin color is inherited from a number of genes.

SOLUTION: genes

PROBLEM: Sentence1: faulting of rock in Earth 's crust causes earthquakes. 
Sentence2: fault movement forms earthquakes.

SOLUTION: earthquakes

PROBLEM: Sentence1: high mountains with well-rounded peaks can be formed by collision of crustal plates. 
Sentence2: Many earthquakes occur when the earth's crustal plates grind and shift along one another.

SOLUTION:
crustal