Question

pick the best description for a malignant tumor
present in normal brains in small amounts
disturbance of consciousness without evidence of a contusion or structural damage
difficult to remove or destroy completely and continues to grow after surgery
can alleviate symptoms of parkinsons disease

Explanation:

A malignant tumor is characterized by its invasive and aggressive nature. It is not a normal component of the brain (eliminating "present in normal brains in small amounts"). A disturbance of consciousness without evidence of contusion or structural damage (like a concussion) is not related to a malignant tumor. And alleviating Parkinson's symptoms is not a description of a malignant tumor. Malignant tumors are difficult to completely remove or destroy and tend to grow back after surgery due to their ability to invade surrounding tissues and have uncontrolled cell growth.

Answer:

difficult to remove or destroy completely and continues to grow after surgery