Answer: The optimum temperature and pressure.
Step-by-step explanation:
The two characteristics that allows the water to remain in the liquid state is the temperature.
The temperature on the earth is very optimum for the water to remain in liquid state. Though some part of the earth has water in the form of ice and glaciers but it can be converted into water.
The pressure on the earth is optimum for the water to remain in liquid state. This is the reason for the water to remains in liquid state.