Which conditions allows liquid water to exist

answer:

(a) AND (D) are incorrect.

i would say strong gravity, and living things.

Gravity because the gravity allows the water to say at the planets surface, and living things because we need it to survive.

*i say B*

At a pressure of 1 atmosphere (1000 millibars), water is liquid only across the temperature range 273K (0 Celsius) to 373K (100 Celsius). At higher pressures, water can remain liquid over a larger range of temperatures.

As we just said, a main requirement is water, which is necessary for many chemical reactions [source: NASA]. Liquid water allows for chemicals to be transported or dissolved, so we do need the water to be between 59 and 239 degrees Fahrenheit (15 and 115 degrees Celsius) so it doesn't vaporize or freeze [source: NASA].

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.