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.

Sentence1: Sand and mud are examples of sediments. 
Sentence2: layers of sand over the remains of organisms over time can create fossils.
Sand

Sentence1: a greenhouse is used to protect plants by keeping them warm. 
Sentence2: Flower size varies by plant.
plants

Sentence1: protein is used to repair cells by the human body. 
Sentence2: DNA makes proteins, proteins build cells, and cells make up people.

protein