when the parent class has only one child class.In other word, when base class have formed only one derived class is knows as Singal Inheritance .
syntax :
class Base
{
    // BODY OF THE BASE CLASS
};
    class Derived : acess_specifier Base
{
   // BODY OF THE DERIVED CLASS
};
Q1.) Example of Single Inheritance .
#include < iostream>
using namespace std;
class Account {
public:
float salary = 60000;
};
class Programmer: public Account {
public:
float bonus = 5000;
};
int main(void) {
Programmer p1;
cout<<"Salary: "<< p1.salary<< endl;
cout <"Bonus: "<< p1.bonus << endl;
return 0;
}