When I click on main site in SharePoint 2013, as shown below, subsite C is duplicated. This is not needed. How to prevent this? I am noob to SharePoint 2013. Please advice.
+ Site Collection
| +--+ Site One
| |
| +--+ Subsite A
| | |
| | + Subsite B
| | |
| | + Subsite C
| |
| + + Subsite C
| | |
| | + Subsite C