单项选择题
A. A Risky Trip Up Mount Everest B. Pollution on Mount Everest C. Mount Everest—Clean-up Effort D. Robert Hoffman and His Clean-up Team
A.history B.date C.beginning D.development
A. The Association Between Color and Mood B. The Difference Between Color and Mood C. Mood’s Influence on Color D. Color’s Influence on Mood