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
Because the sea weed
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The ceremony was rubbish - but the reception was brilliant.
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When it came time to pay, the skunk didn't have a scent, the deer didn't have a buck so they put the meal on the duck's bill.
or
Use a sea saw.
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A multiplication table.
or