"I am a humanoid but I am not a human."
Translation:yoq jIH 'ach Human jIHbe'.
Think of tera'ngan as Earthling as it's used in science-fiction. An alien could technically call a whale from Earth an Earthling, but the word really means "human from Earth." Actually, I wouldn't be surprised if Klingons called humans from, say, the Moon, or even Deneva, tera'ngan.
For the purpose of this course, I guess the creators expect you to translate tera'ngan as Terran or Earthling, but not as human. In the "real" world, I doubt the lines would be drawn so starkly.