根据题意，得
x-4≥0，
解得，x≥4．
故答案是：x≥4．
水工建筑物竖向设计地震加速度代表值应取水平设计地震加速度代表值的（）。
A.1／4
B.1/2
C.1／3
D.2/3
If the variables, X, Y, and Z take on only the values 10, 20, 30, 40, 50, 60, or 70 with frequencies indicated by the shaded regions above, for which of the frequency distributions is the mean equal to the median
