Time complexity in C++ Stl quiz II , q3

Q3) C++ Stl quiz II

Predict the time complexity of the following recursive function, given the vector is of size N and the initial call is calSum(v, 0).

int sum = 0;
void calcSum(vector v, int i)
{
if(i == v.size())
return;
sum += v[i];
calcSum(v, i+1);
}

The given answer is O(N^2) , but how ? it should be O(N)

hi @snehacpcb_6a154f5c45187387 calcSum is passing v by value so its getting copied everytime hence o(N2)