$$If\ r-s=240,\ does\ r=320?$$
Statement 1: r = 4s
From the question stem, r - s = 240
4s - s = 240
3s = 240
s = 240/3 = 80
If r = 4s
r = 4 * 80 = 320
Since r = 320, it answers our target question. Therefore, statement 1 is SUFFICIENT.

Statement 2: s = 80
From the question stem, r - s = 240
r - 80 = 240
r = 240 + 80
r = 320
Since r = 320, it answers our target question. Therefore, statement 2 is SUFFICIENT.

From above, each statement alone is SUFFICIENT, so, therefore, option D is the correct answer.