1. A water-insoluble substance X has been shown to ameliorate the symptoms of Parkinson's disease in human, but its pharmacological mechanism has not yet clear. To investigate its mechanism in animals, the experimental group(s) should include animals that receive injection of (A) only substance X group (B) substance X and physiological saline groups (C) substance X and distilled water groups (D) substance X and the solvent that used for dissolve substance X groups.