What is the worst case complexity of the following code fragment?

void doSomething( int k );

// Assume that function doSomething(k) has a linear time complexity proportional to k, or O(k).

for(i = 0; i < N; i++)

{

for(j = N; j > 0; j--)

{

doSomething( N );

}

}

A.O(N³)

B.O(2^N)

C.O(N²)

D.O(N log N)