Nicole made the model shown below to represent the steps in the formation of a thunderstorm. The diagram has six boxes. The first box on the top left has the symbol '?' in it, an arrow points from it, over to the left to a box with the text 'Meets coool air'; this box has an arrow pointing down from it to a box with the text 'Condenses'; this box has an arrow pointing to the left to a box with the text 'Clouds formed'; this box has an arrow pointing to the left to a box with the text 'Clouds grow bigger'; and this box has an arrow pointing down from it to a box with the text 'Precipitation'.

Which of these best fits the empty cell in Nicole's model?

warm, moist air rises
warm, dry air descends
water vapor condenses in clouds
water vapor evaporates from ocean