pthread function from a class

Let’s say I have a class such as

class c { 
    // ...
    void *print(void *){ cout << "Hello"; }
}

And then I have a vector of c

vector<c> classes; pthread_t t1;
classes.push_back(c());
classes.push_back(c());

Now, I want to create a thread on c.print();

And the following is giving me the problem below: pthread_create(&t1, NULL, &c[0].print, NULL);

Error Ouput: cannot convert ‘void* (tree_item::)(void)’ to ‘void*
()(void)’ for argument ‘3’ to ‘int pthread_create(pthread_t*, const
pthread_attr_t*, void* ()(void), void*)’

pthread function from a class