In each series, look for the degree and direction of change between the numbers. In other words, do the numbers increase or decrease, and by how much?\nLook at this series: 1, 5, 7, 3, __, 1 ...Which number is missing?\nOptions:\n(A) 2\n(B) 4\n(C) 12\n(D) 0\n(E) 13
Let's be accurate as possible and think first.
(E)
E\n13\nThis is an alternating addition and subtraction series.

In the first pattern, 6 is added to each number to arrive at the next.

In the second, 2 is subtracted from each number to arrive at the next.

.

The final answer: (E)