A class has tree teachers, Mr. `X`, Ms.`Y` and Mrs.`Z` and six students `A`, B`, `C`, `D`, `E`, `F`. Number of ways in which they can be seated in a line of `9` chairs,if between any two teachers there are exactly two students is
A. `18xx6!`
B. `12xx6!`
C. `24xx6!`
D. `6xx6!`