1. "_______ libro" (this book, near me):
Answer: Este
Explanation: "Libro" is masculine singular and the thing is near the speaker: ESTE libro. "Esto" is the neuter form and never goes before a noun.
3. "¿Me pasas _______ tijeras?" (those scissors, near you)
Answer: esas
Explanation: "Tijeras" is feminine plural and near the listener: ESAS tijeras. "Aquellas" would mean far from both people.