There will be an error when you run the program below. What's the problem?

Question

namespace ConsoleApplication1
{
class A
{
protected int x = 123;
}
class B : A
{
static void Main()
{
A a = new A();
B b = new B();

a.x = 10;
b.x = 10;
}
}
}

Answer 1

Don't write protected in firs of integer

Answer 2

Maybe this can help to explain

https://www.sololearn.com/learn/CSharp/2679/?ref=app