Seven boxes P, Q, R, S, T, U and V are kept one over the other but not necessarily in the same order. S is kept third from the bottom. Only V is kept between P and S. Only three boxes are kept between T and V. T is kept immediately below U. Q is kept immediately above S. R is kept third from the top. How many boxes are kept between U and S?
AThree
BOne
CTwo
DFour