Changed an to a (#10851)

Author: martingbrown

docs/framework/wcf/basic-wcf-programming.md

@@ -26,7 +26,7 @@ This section presents the fundamentals for creating Windows Communication Founda
  Describes the basics of hosting services in an application.  
 
  [Building Clients](../../../docs/framework/wcf/building-clients.md)  
- Describes how to obtain metadata from services, convert that into WCF client code, handle security issues, and build, configure, and host an WCF client.  
+ Describes how to obtain metadata from services, convert that into WCF client code, handle security issues, and build, configure, and host a WCF client.  
 
  [Introduction to Extensibility](../../../docs/framework/wcf/introduction-to-extensibility.md)  
  Describes how to extend WCF to create custom solutions.