Consider the routine below which checks whether there are two values in an array which sum to `21`. Determine the run-time complexity of the routine using Big-O notation.

def check_for_sum(myArray):
  for element_a in myArray:
    for element_b in myArray:
      if element_a + element_b == 21:
        return TRUE

  return FALSE

The algorithm as written above has a run-time complexity of Select an answer O(n) O(n^3) O(1) O(2^n) O(n^2) O(log(n)) O(n!)