单项选择题
A. Convenient. B. Luxurious. C. Economic. D. Modern.
A. Birds with duller colors. B. Birds with darker colors. C. Birds with brighter colors. D. Birds with different colors.
A. Trees provided them with shades. B. Trees indicated plenty of sunlight and rainfall. C. Trees were materials for burning and building houses. D. Trees provided them with fruit and food.