Fix introductions (#2198)

concepts/attributes/introduction.md

@@ -15,4 +15,4 @@ class MyClass
 
 This declarative metadata only associates additional structured information to the code and does not modify its behavior, but that metadata is used by other part of the code to change how its target would behave or add, change or remove, restrict some its functionalities.
 
-There are many [predefined and reserved attributes](https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/attributes/general#conditional-attribute), for example: `Flags`, `Obsolete`, `Conditional`, each has a specific that can be looked up on the C# documentation. Note that the full name of an attribute like [`Flags`](https://docs.microsoft.com/en-us/dotnet/api/system.flagsattribute
+There are many [predefined and reserved attributes](https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/attributes/general#conditional-attribute), for example: `Flags`, `Obsolete`, `Conditional`, each has a specific that can be looked up on the C# documentation. Note that the full name of an attribute like [`Flags`](https://docs.microsoft.com/en-us/dotnet/api/system.flagsattribute)

concepts/do-while-loops/about.md

@@ -1,6 +1,6 @@
 # About
 
-To repeatedly execute logic, one can use loops. If the code in a loop should always be executed at least once, a `do/while` loop can be used:
+To repeatedly execute logic, one can use loops. If the code in a loop should always be executed at least once, a `do`/`while` loop can be used:
 
 ```csharp
 int x = 0;

concepts/do-while-loops/introduction.md

@@ -1,6 +1,6 @@
 # Introduction
 
-A less commonly used alternative to the above syntax is a `do-while` loop:
+If the code in a loop should always be executed at least once, a `do`/`while` loop can be used:
 
 ```csharp
 int x = 23;

concepts/flag-enums/introduction.md

@@ -2,7 +2,7 @@
 
 The C# [`enum` type](https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/builtin-types/enum) represents a fixed set of named constants (an enumeration).
 
-Normally, one `enum` member can only refer to exactly one of those named constants. However, sometimes it is useful to refer to more than one constant. To do so, one can annotate the `enum` with the [`Flags` attribute](https://docs.microsoft.com/en-us/dotnet/api/system.flagsattribute
+Normally, one `enum` member can only refer to exactly one of those named constants. However, sometimes it is useful to refer to more than one constant. To do so, one can annotate the `enum` with the [`Flags` attribute](https://docs.microsoft.com/en-us/dotnet/api/system.flagsattribute)
 
 A flags enum can be defined as follows (using binary integer notation `0b`):
 

exercises/concept/attack-of-the-trolls/.docs/introduction.md

@@ -15,9 +15,9 @@ class MyClass
 }
 ```
 
-This declarative metadata only associates additional structured information to the code and does not modify its behavior, but that metadata is used by other parts of the code to change how its target would behave or add, change or remove, restrict some its functionalities.
+This declarative metadata only associates additional structured information to the code and does not modify its behavior, but that metadata is used by other part of the code to change how its target would behave or add, change or remove, restrict some its functionalities.
 
-There is many [predefined and reserved attributes](https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/attributes/general#conditional-attribute), for example: `Flags`, `Obsolete`, `Conditional`, each has a specific that can be looked up on the C# documentation. Note that the full name of an attribute like [`Flags`](https://docs.microsoft.com/en-us/dotnet/api/system.flagsattribute)
+There are many [predefined and reserved attributes](https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/attributes/general#conditional-attribute), for example: `Flags`, `Obsolete`, `Conditional`, each has a specific that can be looked up on the C# documentation. Note that the full name of an attribute like [`Flags`](https://docs.microsoft.com/en-us/dotnet/api/system.flagsattribute)
 
 ## Flag Enums
 

exercises/concept/interest-is-interesting/.docs/introduction.md

@@ -30,7 +30,7 @@ while (x > 10)
 
 ## Do While Loops
 
-A less commonly used alternative to the above syntax is a `do-while` loop:
+If the code in a loop should always be executed at least once, a `do`/`while` loop can be used:
 
 ```csharp
 int x = 23;

exercises/concept/tim-from-marketing/.docs/introduction.md

@@ -61,10 +61,10 @@ The `??` operator allows one to return a default value when the value is `null`:
 
 ```csharp
 string? name1 = "John";
-name1 ??= "Paul"; // => "John"
+name1 ?? "Paul"; // => "John"
 
 string? name2 = null;
-name2 ??= "George"; // => "George"
+name2 ?? "George"; // => "George"
 ```
 
 The `?.` operator allows one to call members safely on a possibly `null` value: