Minor grammar fix in introduction.md

concepts/booleans/introduction.md

@@ -1,5 +1,5 @@
 # Introduction
 
-Booleans in C# are represented by the `bool` type, which values can be either `true` or `false`.
+Booleans in C# are represented by the `bool` type, whose values can be either `true` or `false`.
 
 C# supports three boolean operators: `!` (NOT), `&&` (AND), and `||` (OR).