if statements with more than once condition

int a = 10;
int b = 10;
int c = 10;
int d = 10;

int x = a + b + c + d;

Random random = new Random();
int numberFinder = random.Next(0, x);

string 1 = "The number is 10 or lower";
string 2 = "The number is between 11 and 20";
string 3 = "The number is between 21 and 30";
string 4 = "The number is 31 or higher";

if ( numberFinder <= a )
{
    Console.Writeline(1);
}
else if ( numberFinder ????????????????????