From II, we conclude that P is R's mother.

From I, we conclude that M is the brother or sister of P's husband, who is also R's father. Thus, R is either nephew or niece of M.

From II, we know that N is K's son and K is B's grandfather. Thus, N is the son of B's grandfather i.e. N is either father or uncle of B.

From I, B is the daughter of M. So, M is either father or mother of B.

Clearly, the correct relationship between M and N cannot be deduced.

From II, we conclude that in a class of 40, Deepak ranks 23rd from the bottom i.e. 18th from the top.

From I and II, we find that Suman is 3 ranks below 18th rank from the top i.e. she ranks 21st from the top.

From II and III, we find that Suman is 3 ranks above 23rd rank from the bottom

i.e. she ranks 20th from the bottom or 21st from the top.

From I, the order is : E, B, C or C, B, E.

From II, the order is : E, B.

From III, the order is : A, D, E.

Combining the above three, we get the order as : A, D, E, B, C. Clearly, E is sitting in the middle.

Observing I, II and III, we find that similar letters have similar code symbols at the corresponding places in the code. So, this is direct-coding.

Thus, to find the code for DATE, we need the code for D which can be obtained from I only (i.e. $.) and the codes for A, T and E which can be obtained either from II or III (@, # and % respectively).

From II, we know that Copal's brother was born in 1982.

From III, we find that Gopal's brother was 8 years younger to him i.e. Gopal was born in 1974.

From I, we find that Sanjay is 6 years older than Gopal. Thus, Sanjay was born in 1968.

From I, we have: M > V, V > S, V > N ...(i)

From II, we have: Mukul is the oldest ...(ii)

From III, we have: S > N ...(iii)

Combining (i) and (iii), we get :M > V, V >S > N or M>V > S > N. Clearly, Nikunj is the youngest.

To find the code for 'we', we need to have any of the following:

(i) 'We are friends' should have only 'We' common with another statement, as in II;

(ii) 'We are friends' should have only 'are' and 'friends' common with another single or two statements, as in I and III. Thus, we need Either II only or I and III only.

From the given statement, the descending order of heights is :__, Q,__, S,__.

From II, we have the order: _, Q, R, S,__. Thus, R is in the middle.

From III, we have the order : P, Q,__, S,__. But, according to I, T is not the shortest.

So, R is the shortest. Thus, we have the order : P, Q, T, S, R. So, T is in the middle.

From I and II, we conclude that Mathematics period began at 9.00 a.m., Biology period began at 8.00 a.m. and Physics period began at 11 a.m. So, the Chemistry period began at 10.00 a.m.

From I and III, we conclude that Mathematics period ended and Chemistry period began at 10.00 a.m.