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: Silica sand is primarily mined from sandstone deposits. 
Sentence2: erosion forms silica sand.

SOLUTION: Silica

PROBLEM: Sentence1: Female monotremes lack a uterus and vagina. 
Sentence2: Babies are normally delivered from the uterus through the vagina.

SOLUTION: uterus

PROBLEM: Sentence1: landfills have a negative impact on the environment. 
Sentence2: Most municipal trash is disposed of in such landfills.

SOLUTION:
landfills