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

SOLUTION: Sand

PROBLEM: Sentence1: Average vehicle speed rises by only 0.3 miles per hour. 
Sentence2: a speedometer measures miles per hour.

SOLUTION: hour

PROBLEM: Sentence1: Vertebrate chordates have a backbone. 
Sentence2: birds have a backbone.

SOLUTION:
backbone