Acute gastritis is an inflammation of the mucosa. It is transient, may involve local irritants such as aspirin: food contamination, caffeine, alcohol. It is self- limiting and is very serious.

A. Brain, blood, cerebrospinal fluid (CSF): These are the three main components within the cranial vault as described by the Monro-Kellie doctrine. The total volume of these components remains constant, and any increase in one must be offset by a decrease in another to prevent elevated ICP.

B. Cerebrospinal fluid (CSF), blood, oxygen: While CSF and blood are intracranial components, oxygen is not a physical substance occupying volume in the cranial cavity. It is transported within the blood and does not contribute to changes in ICP in terms of physical space.

C. Brain, cerebrospinal fluid (CSF), air: Air is not a normal component of the cranial cavity. The presence of air would indicate pathology, such as a skull fracture with pneumocephalus, which is abnormal and can contribute to increased ICP but is not a standard component.

D. Brain, blood, lymphatic fluid: While the brain and blood are correct components, the central nervous system, including the brain, does not have a conventional lymphatic system like other parts of the body. Waste products are primarily cleared by the glymphatic system, which utilizes CSF, rather than traditional lymphatic fluid.

A. Three: Up to three bowel movements per day is generally considered the upper limit of normal for stool frequency in adults. This range accommodates individual variation while distinguishing normal from diarrhea.

B. Five: Five stools per day exceed the typical upper limit and may indicate diarrhea or an underlying gastrointestinal disorder if persistent, rather than normal bowel habits.

C. Two: Two stools per day fall well within the normal range but do not represent the upper limit. Normal stool frequency can range from three times per day to three times per week.

D. Seven: Seven stools per day indicate frequent bowel movements consistent with diarrhea, which is above normal frequency and warrants further assessment for underlying causes.