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: a flashlight converts chemical energy into light energy. 
Sentence2: Only as long as there are batteries in the flashlight, the flashlight will function.

SOLUTION: flashlight

PROBLEM: Sentence1: Here, the lungs supply the blood with oxygen. 
Sentence2: Brain cells die quickly if their blood supply is cut off.

SOLUTION: blood

PROBLEM: Sentence1: Output of the fan is varied by means of a series of adjustable vanes upstream of the impeller. 
Sentence2: fan speed is adjustable.

SOLUTION:
adjustable