General Studies · Linear Arrangement (Box Puzzle)

Seven boxes, C, D, E, F, X, Y and Z, are kept one over the other but not necessarily in the same order. No box is kept above Z. Only three boxes are kept between Z and Y. Only one box is kept between F and E. E is kept immediately above Y. Only four boxes are kept between F and X. C is kept at some place above D. Which box is kept second below C?