Operators - General Questions

What is the output of the following program?

string s = null;
string t = s ?? "default";
Console.WriteLine(t);

Which operator converts a reference safely, returning null if the cast fails?

What is the output of the following program?

int a = 5;
int b = a++;
Console.WriteLine(a + " " + b);

What is the output of the following program?

bool f = false;
Console.WriteLine(!f && (3 > 2));

What is the output of the following program?

int x = 7;
Console.WriteLine(x > 5 ? "big" : "small");