There are five books of different thickness. A is thicker than C and B is thicker than D. E is not as thick as B, but is thicker than C. D is not as thick as C. Which is the thinnest book?

A > C  -----(i),   B > D  -----(ii),  E < B  --------(iii),  E > C  ---------(iv),  C > D  ---------(v)

from (i) and (v),   we get    A > C > D   ---------(I)

from (iii) and (iv), we get    B > E > C    --------(II)

From (I) and (II) , it is clear that 'D' is the thinnest.