Kelvin Is Teaching His Students a Short, New Song

Kelvin is teaching his students a short, new song. First, he teaches them the words to the whole song. Then he teaches them the melody using his guitar. Then he asks the class to sing along with him, but almost all of them are lost and stop singing after the first few notes. What did Kelvin do wrong?

A) He taught the melody and words separately.
B) He failed to break the song into sections.
C) He used a guitar, which makes it difficult to observe reactions.
D) He did not know the song well before teaching it.