C. No.
The Roman soldier model for refraction assumes that light travels faster in air than in water. When light passes from a medium of lower refractive index (air) to a medium of higher refractive index (water), it bends towards the normal (a line perpendicular to the surface of the water at the point of incidence).
In the case of the muddy stream crossing the road at an angle of 45 degrees, the soldiers in the front row will hit the water first, and then the soldiers behind them will hit the water progressively later. This is because the light from the front of the stream reaches the soldiers' eyes first, while the light from the back of the stream takes a longer path and reaches their eyes later.
Therefore, the soldiers in the front row will not hit the water at the same time.