P, Q, R, S, T, U and V are sitting in a row facing North. In order to determine, who is sitting exactly in the middle of the row, which of the following information is needed? 

• T and U are sitting at extreme ends of the row 
• S is third to the right of T 
• Q is four places to the left of R and P is two places to the left of V

We need to find who sits in the middle (position 4) among 7 persons.

Using I + II:

T and U are at the extreme ends. If T is at the right end, S cannot be 3rd to the right (out of row). So T must be at the left end, and S becomes position 4 (middle).
Middle = S

Using I + III:

With T and U fixed at the ends, Q must be 4 places left of R, so only possible is Q at position 2 and R at position 6. Also P is 2 places left of V, so P at position 3 and V at position 5. The remaining person S automatically comes at position 4.
Middle = S

Conclusion: Statement I along with either II or III is sufficient.

Correct Option: 3) I and either II or III are sufficient