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答案：C
解析：
The fact that function f of x less than or equal to u for all values of x means that the point P (t，u) is the maximum of the quadratic function f, so P (t，u) must be the vertex of the parabola. The parabola intersects the x-axis at the points (1，0) and (4，0), so t must be halfway between 1 and 4. Therefore, t = 1 + ((4 minus 1) over 2) = 2.5. Of the choices, the only one with x-coordinate equal to 2.5 is (2.5，3). Therefore, (2.5，3) could be the coordinates of point P.
