完形补文：下面的短文有10处空白,每处空白后的括号内有一个词,请根据短文内容将其正确的形式填入文中,以恢复文章原貌。 Can Dogs See Colors? Man's best friend is colorblind (色盲). Fortunately (fortunate), his (survive) does not depend upon the ability to see colors. The (sharp) of his sense of smell makes up for his (fail) to see colors. It helps him to tell between things. (study) support the conclusion that dogs live in a (color) world. The testing done primarily (focus) on the dogs' responses to colors for food. Dogs could not tell the (differ)between one color signal for food, and other colors that were not for food. Most animals’ lack of ability to see colors can be (easy) understood. Many colorblind animals hunt for food in the dark of night. Their other senses have highly (develop). Thus their lack of color vision does not affect them. Other animals with color vision are (monkey) and apes (猿). Both can be trained to open a colored door, behind which is food.