Complete the exhausted college student's complaint about her backpack weight.

"I don't know why the professor assigned _____ massive textbook," groaned Sarah, dropping the 10-pound book directly onto her desk with a loud thud.

The correct answer is this.

"This" is used for a singular object that is physically close to the speaker (like a book she was just holding and dropped on her own desk). "That" would be used if the book were far away.