OOP | Question

What is the problem with this code :

struct Counter {
    int count;
};

void increment(Counter c) {
    c.count += 1;
}

int main() {
    Counter clock = {1};
    increment(clock);
}

we cannot define a struct with only one attribute

the clock variable must actually be instantiated like this : Counter clock {1};

the clock variable is not modified by the increment function

the main function does not have a return statement