Here are the correct answers to your questions:
Question 11:
Laura está en la clase de español.
Answer: está
Question 12:
Los relojes están encima de la puerta.
Answer: están
Question 13:
¡Hola! ¿Cómo está usted hoy?
Answer: está
Question 14:
This is the way to say SOME chairs in Spanish.
Answer: Unas sillas
Question 15:
This is the way to say THE students in Spanish.
Answer: Los estudiantes
Question 16:
These are the MASCULINE articles in Spanish and mean a/an/some/few.
Answer: Un, Unos
Question 17:
These are the FEMININE articles and mean THE in Spanish.
Answer: La, Las
Question 18:
This is the correct way to make 'El lápiz' plural in Spanish.
Answer: Los lápices
Question 19:
This is the correct way to make 'La bandera' plural in Spanish.
Answer: Las banderas
Question 20:
This is the correct way to make 'El papel' plural in Spanish.
Answer: Los papeles
If you have any more questions or need further assistance, feel free to ask!