Eliza tried humming it before she tried to sing the song.
It's D second because the reason before the says "One is that..."
The correct answer is "Slang displays a tone that is too casual"
Slang speak is highly informal, sometimes even offensive. One should never use slang in a business setting because business deals should be kept highly informal and professional. Slang shouldn't be used under any circumstance as it may insult the people with whom we are talking by making it seem that we don't appreciate them or their business endeavors.
