Hi sanchu,

Bill has correctly explained the logic behind the prompt. I'm going to present the information in a slightly different way (using the vocabulary the prompt uses):

Let's say that the "first level" of a phenomenon is N.

So, the "second level" would be 10 times the "first level" = 10N
The "third level" would be 10 times the "second level" = 10(10N) = 100N
The "fourth level" would be 10 times the "third level" = 10(100N) = 1,000N
Etc.

The pattern is that each level is "10 times" greater than the prior level. With that pattern, a "reading of 8" relative to a "reading of 3" is a difference of 10(10)(10)(10)(10)N = (N)10^5

Final Answer: C

GMAT assassins aren't born, they're made,
Rich