Subjects+Can+Be+Complimented+with+a+Secondary+Element

As every good photography knows, there should only be one subject or point of interest in a photo. But it is ok, and often necessary, to include a secondary, less important element that compliments the main focal point. For example, if I am taking a photo of a duck, it is okay to include the pretty water lily in the photo as well. I wouldn't, however, want to include an empty bottle floating along the surface with my duck. The bottle is not a complementary element, it is a distraction.