Update introduction.md (#2410)

Author: BNAndras

exercises/concept/land-grab-in-space/.docs/introduction.md

@@ -2,7 +2,7 @@
 
 ## Structs
 
-C# `struct`s are closely related `class`s. They have state and behavior. They have constructors that take arguments, instances can be assigned, tested for equality and stored in collections.
+C# `struct`s are closely related to `class`es. They have state and behavior. They have constructors that take arguments, instances can be assigned, tested for equality and stored in collections.
 
 ```csharp
 enum Unit