D) Muscle tenseness in almost the entire abdomen is the correct answer. A ruptured appendix typically causes severe abdominal pain, with the main symptom being muscle tenseness or rigidity in the entire abdominal area. This is due to the inflammation and irritation of the abdominal lining (peritoneum) caused by the leakage of digestive juices and bacteria from the ruptured appendix. The other answer choices do not accurately describe the main symptoms of a ruptured appendix. Extreme sweating, reddening skin, dilated pupils, and shallow breathing are not common indicators of this condition. Diarrhea and frequent urination may occur, but are not the primary symptoms.