A、It’s the work combined musical talents with expertise. B、It’s the song published in a collection. C、It’s the masterpiece enjoy

The story of how the song " Happy Birthday to You" came to be, began as a sweet one, that later soured. Two sisters, Mildred Hill, a teacher at the Louisville, Kentucky Experimental Kindergarten, and Dr. Patty Hill, the principal of the same school, together wrote a song for the children, entitled " Good Morning to All".(19)When Mildred combined her musical talents, as the resident expert on spiritual songs, with her sister’s expertise in the area of Kindergarten Education, "Good Morning to All" was sure to be a success.
    The sisters published the song in a collection entitled " Song Stories of the Kindergarten" in 1893. Thirty-one years later, after Dr. Patty Hill became the head of the Department of Kindergarten Education at Columbia University’s Teacher College, a gentleman by the name of Robert H. Coleman published the song, without the sisters’ permission. What’s worse for the sisters is(20)he added a second verse, the familiar " Happy Birthday to You".
     (20)Mr. Coleman’s addition of the second verse popularized the song and, eventually, the sisters’ original first verse disappeared. " Happy Birthday to You" , the one and only birthday song, had altogether replaced the sisters’ original title, "Good Morning to All".
     (21)After Mildred died in 1916, Patty, together with a third sister named Jessica, sprang into action and took Mr. Coleman to court. In court, they proved that they, indeed, owned the melody. Because the family legally owns the song, it is entitled to royalties from it, whenever it is sung for commercial purposes.
19. Why was "Good Morning to All" sure to be a success?
20. How did the song become popular?
21. How did Patty and Jessica do in court?