If Z sits directly opposite X, which executive must sit next to U ? 

When they hold a meeting seven company executives - T, U, V, W, X, Y and Z - sit at a rectangular table. Three executives sit along one side of the table, and three sit along the other side, each directly opposite one of the other three. The seventh sits at the head of the table; There is no seat at the foot of the table. U always sits in one of the two seats farthest from the head of the table. Y and V always sit next to each other. V never sits next to Z. If does not sit at the head of the table, W sits there.