• Teacher: Tell me a way to prevent a disease which is caused by biting insects. 
  Student: Don’t get bitten by them.

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• The teacher is explaining to the student, “If you see someone sinking in the water, you should pull his hair to save him from the water. It will be easy for you.’ Student: But sir, if it happens to you, we shouldn’t help you. Teacher: why? Student: Because you don’t have any hair.