In this type of questions, some clues are given regarding the order of occurrence of certain events. The candidate is required to analyse the given information, frame the right sequence and then answer the questions accordingly.

Seven executives P, Q, R, S, T, U andW reach office in a particular sequence.
U reaches immediately before P but does not immediately follow S. R is the last one to reach office. T follows immediately after P and is subsequently followed by W.

Among the executives, who reaches the office first ? 

A. Q
B. S
C. U
D. Can't be determined
E. None of these
Answer: B . S


Clearly, U is followed by P;  P by T;  T by W.
Now, U does not immediately follow S and R reaches last.
So, the order of reaching office is : S, Q, U, P, T, W, R.

S is the first to reach office.