What is the code for a loop that iterates from the end of a string toward the beginning?

a. string::reverse_iterator i{s.begin()};
while (i != s.end())
{
cout << *i;
++i;
}
b. string::reverse_iterator i{s.rbegin()};
while (i != s.rend())
{
cout << *i;
++i;
}
c. string::reverse_iterator i{s.end()};
while (i != s.begin())
{
cout << *i;
--i;
}
d. string::reverse_iterator i{s.rbegin()};
while (i != s.rend())
{
cout << *i;
--i;
}

d. string::reverse_iterator i{s.rbegin()};
while (i != s.rend())
{
cout << *i;
--i;
}