There are five questions below，

A ballroom dance competition will be held between two teams, the Green team and the Red team．The Green team consists of couple H, couple I, and couple K．The Red team consists of couple X, couple Y, and couple Z． During the competition, each team will perform three types of dances—the fox-trot, the tango, and the waltz． Each couple on each team will perform exactly one of the three types of dances．At any one time, only one couple will be performing, but the six couples can perform in any order until all dances have been performed．The following rules also apply to the competition： The same type of dance cannot be performed twice in succession.

Couple H cannot dance the waltz．

Couple I cannot dance the tango．

Couple Y must dance the waltz．

If couple K dances a fox-trot, which of the following couples must dance a tango？

Which of the following could be the schedule for the competition's first three dances？

If the competition schedule strictly alternates couples on the Green team with couples on the Red team, and if couple Y dances fourth, then a waltz must be performed.

If the third through the sixth dances in the competition are the fox-trot, the tango, the waltz, and the tango, respectively, then couple X can perform in any of the following positions EXCEPT.

Assume that the order of the couples, from first to sixth, has been established as X, Y, Z, H, I, and K．If couple X performs a fox-trot, which of the following couples must also perform a fox-trot？