To convert from km/h to m/s, we need to multiply by a conversion factor.
We know that 1 km = 1000 m and 1 hour = 3600 seconds.
So, 1 km/h = \(\frac{1000\text{m}}{3600\text{s}}\) = \(\frac{5}{18}\) m/s.
Therefore, to convert x km/h to m/s, we multiply by \(\frac{5}{18}\) to get y.
So, y = \(\frac{5}{18}\)x.
Therefore, option D, \(\frac{5}{18}\)x, is the correct answer.