Which of the following statements is correct about namespaces in C#.NET?

• Namespaces can be nested only up to level 5.
• A namespace cannot be nested.
• There is no limit on the number of levels while nesting namespaces.
• If namespaces are nested, then it is necessary to use using statement while using the elements of the inner namespace.
• Nesting of namespaces is permitted, provided all the inner namespaces are declared in the same file.