Because sometimes you can get rid of cancer.
or
Three. One to climb the ladder while the second kicks the ladder out from under her. And the third to say, "I knew that was too high for you dear."
or
None. Agnostics question whether electricity really exists.
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A sponge!
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Because E.T. eventually went home!
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None. They will never find a bulb that burns as brightly as the old one.
or