An ideal passive filter has a linear gain of 1 (that means no gain, no losses). If it has a ripple of δ, means the maximum gain will be 1 and the minimum will be (1-δ). The ripple is maximum-minimum= 1 - (1-δ) = δ.
If you cascade M cells, then the maximum gain will be 1^M,
while the minimum will be (1-δ)^M.
So the total ripple will be 1^M - (1-δ)^M = 1 - (1-δ)^M --> that is answere A)