premise: In a single day, exactly seven trucks—S, T, U, W, X, Y, and Z—are the only arrivals at a warehouse. No truck arrives at the same time as any other truck, and no truck arrives more than once that day. Each truck is either green or red (but not both). The following conditions apply: No two consecutive arrivals are red. Y arrives at some time before both T and W. Exactly two of the trucks that arrive before Y are red. S is the sixth arrival. Z arrives at some time before U. For which one of the following pairs of trucks is it the case that they CANNOT both be red?
hypothesis: X and Z