Necesitan is the answer
hope i had helped.
These sentences can be complete in the following way:
1) Nadie.- this would mean that you do not know anyone.
2) Ningún- it makes reference to the book. you do not have a book
3) nunca. This means that you do not do that activity. you never do it
4) ni. not having one thing nor the other.
5) nada. this means that the table is empty- nothing on it.
Answer:
1. Sobrino 2. Primos 3. Abuelita 4.Sobrina
El avion aterriza rapidamente en la pista.