Solution: If the rotated OAn coincides with the positive semi-axis of the Y axis, then the rotation angle of the ray OA is: 360? K+90, (k is a positive integer)

Therefore, the rotation angle must be a multiple of 10;

From the meaning of the title: 2+22+23+24=30, 25+26+27+28 = 480;

That is, the value of n must be a multiple of 4, which obviously does not meet the meaning of the question;

A when n= 16, the rotation angle is: 510× (16÷ 8) =1020.

That's 360? K+90 = 1020, and the obtained k value is not a positive integer, so option a does not meet the meaning of the question;

B, when n=24, the rotation angle is 5 10× (24 ÷ 8) = 1530,

That's 360? K+90 = 1530, and the solution is k=4, so option b meets the meaning of the question;

D, obviously 32 > 24, has proved that option B meets the meaning of the question, so option D must not meet the meaning of the question;

So choose B.

This problem is mainly solved by exclusion. It is difficult to correctly express the rotation angle of light OA, and it is also difficult to correctly judge that n is a multiple of 4.