Which condition has the effect of reducing critical engine failure speed?

The reason slush on the runway or inoperative antiskid reduces critical engine failure speed is tied to the impact it has on aircraft performance during takeoff. Critical engine failure speed is the minimum speed at which an aircraft can maintain controlled flight with one engine inoperative. When slush is present on the runway, it can create a slippery surface that affects the aircraft's ability to accelerate and maintain directional control. Therefore, during takeoff, pilots may decide that the reduced traction calls for a lower speed at which they can safely reject the takeoff and still maintain control of the aircraft if an engine fails.

Conversely, the other conditions mentioned do not directly lead to a reduction in critical engine failure speed. High density altitude affects engine performance and lift but does not inherently impact the critical engine failure speed in the same manner. Low gross weight can improve performance characteristics, but it doesn't directly correlate to a lower critical engine failure speed. High winds can affect the takeoff scenario but are more about flight handling and may not serve to reduce critical engine failure speed in the same way that slush and runway conditions do.