No.# The solution meet the goal, the response is wrong.
To try :
int[] intArray ={1,2,3,4,5};
int sum = 0;
for(int i=0;i<intArray.Length;)
{
sum +=intArray[i];
intArray[i++]=sum;
}
foreach(var item in intArray){
Console.WriteLine(item);
}

No.# The last should catch all of the exceptions. So the correct order is
A , D, C

No.# From top of code segments, correct answer I think is:
A, B, C

No.# using System;

public class Program
{
static void Main()
{
Class1 class1 = new Class1();
var x = class1?.Method1();
var y = x ?? false;
Console.WriteLine($"x={x}, and y={y}");
}

public class Class1
{
public bool? value;
public bool? Method1()
{
if (value ?? true) { return null; }
else { return true; }
}
}

}

// A) x=null, y=null
// B) x=true, y=true
// C) x=, y=False
// D) x=false y=false

No.# --b: decrease before run the instruction
b--: decrease after running the instruction

No.# Wrong answer.. The correct answer is D

No.# using System;

public class Program
{
public static void Main()
{
int a = 1;
int b = 2;
Console.WriteLine(a == --b && a == b++);

Console.WriteLine(a == --b || a == b++);

Console.WriteLine(a == --b && b == a++);
}
}

True
True
False

No.# The output of line 05 is True is yes

using System;

public class Program
{
public static void Main()
{
int a = 1;
int b = 2;

if (a == --b && b == a++)
{
Console.WriteLine("true");
}
else
{
Console.WriteLine("false");
}
}
}