Read the following information and answer the questions.
An ice-cream maker is experimenting with six chemical essences, U, V, W, X, Y and Z for developing a new flavour called “SEETER and HEALTHIER”. The details of these chemical essences are as follows:
A- U is sweeter than V and healthier than Z.
B- V is sweeter than Y and less healthy than Z.
C- W is less sweet than X and less healthy than U.
D- X is less sweet and healthier than Y.
E- Y is less sweet and healthier than U.
F- Z is sweeter than U and less healthy than W.
Which is the least healthy essence?