Multiple Choice Question Why do we use a while loop with a structured file, instead of the for-line-in-file approach? Comparing line to the empty string helps remove blank lines from the file. We don't know how many pets will be in the input file. We don't know how many treats each pet will get. It is better to use a while loop with the readline approach. | It is better to use a while loop when some lines in the file need to be converted to ints. Multiple Choice Question Assuming that grades refers to (70, 80, 90), select the expression(s) that evaluate to 90. grades [-1] grades [grades. index (90)] grades. popo grades[len(grades) - 1] We've seen that tuples behave much like lists. The following four functions were presented in earlier lecture videos; all four take one or more arguments of type list. Select which function(s) would work if they were passed tuples instead of lists. calculate_average (1st): Return the average of the grades in 1st. double_even_indices (1st): Double every other int in 1st, starting at index 0. shift_left(1st): Shift each item in 1st one position to the left and shift the first item to the last position. sun_itens (listi, list2): Return a new list in which each item is the sum of the items at the corresponding position of list1 and list2