Merge pull request #4737 from Rageking8/merge-code-blocks-for-c2504

Merge code blocks for C2504

Author: ShannonLeavitt

docs/error-messages/compiler-errors-2/compiler-error-c2504.md

@@ -10,7 +10,7 @@ ms.assetid: c9e002a6-a4ee-4ba7-970e-edf4adb83692
 
 'class' : base class undefined
 
-The base class is declared but never defined.  Possible causes:
+The base class is declared but never defined. Possible causes:
 
 1. Missing include file.
 
@@ -23,11 +23,7 @@ The following sample generates C2504:
 // compile with: /c
 class A;
 class B : public A {};   // C2504
-```
-
-// OK
 
-```
-class C{};
-class D : public C {};
+class C {};
+class D : public C {};   // OK
 ```