The following is the instruction to the people who have to take this medicine.     Dosage: Adult twelve years old and over take two teaspoonfuls as needed, not more than fifteen teaspoonfuls per day. Children six years old to twelve years old take half the adult dosage, not more than seven teaspoonfuls per day.     Warning: Do not overtake this medicine unless directed by a doctor. Children under six years old and persons with high blood pressure, heart disease do not take this medicine. This preparation may cause  _ . So do not drive or operate machinery while taking this medicine. Long- time cough is dangerous. If relief does not occur within three days, discontinue use and go to see your doctor. According to the instruction of this medicine, for purposes of dosage, an adult is a person of   _  .
six years old seven years old twelve years old none of the above