Answer:
1.) caused by involuntary contractions of your diaphragm.
2.) pleurisy of the diaphragm, pneumonia, uremia, alcoholism, disorders of the stomach or esophagus, and bowel diseases. They can also be associated with pancreatitis, pregnancy, bladder irritation, liver cancer or hepatitis.
3.) hold your breath and swallow three times, try to breathe into a paper bag, and/or drink a glass of water quickly.
4.) usually last a few minutes and are not a medical concern but, if your hiccups last longer than two days, they're considered chronic.