Six people: A, B, C, D, E, F
1) A is standing at one of the ends of the row.
2) D is standing fourth from the right end.
3) There are two people between D and C.
(Here case 2 gets eliminated)
4) B is second from the left end.
5) E is standing to the immediate left of F.
Hence, four persons are standing to the left of F.