Paragraph: (Science-textbook/science-g4-16.txt)
Sent 1: You approach the door of your friends house.
Sent 2: What is the first thing you do before entering?
Sent 3: Of course, you wipe your feet.
Sent 4: You are a thoughtful visitor.
Sent 5: Fortunately, there is a nice piece of carpet by the door to wipe your shoes.
Sent 6: Too bad your caring comes at a price.
Sent 7: After wiping your feet on the mat you reach out to touch the brass knocker on the door.
Sent 8: A spark suddenly jumps between your hand and the metal.
Sent 9: You feel an electric shock.
Sent 10: Why do you think an electric shock occurs?
Sent 11: An electric shock occurs when there is a sudden discharge of static electricity.
Sent 12: Has this ever happened to you?
Sent 13: You reached out to touch a metal doorknob and received an unpleasant electric shock?
Sent 14: The reason you get a shock is because of moving electric charges.
Sent 15: Moving electric charges also create lightning bolts.
Sent 16: It is also the same reason electric current flows through cables and wires.