Given scientific fact as input, generate the question from this fact such that it can be answered from the input.

Q: Water leaves ponds and lakes through evaporation and also as outflow.

A: Water leaves ponds and lakes through evaporation and also as what?
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Q: Under a crushed sugar cube is added and the water is stirred conditions would a sugar cube dissolve most quickly when placed in a liter of water at room temperature.

A: Under which conditions would a sugar cube dissolve most quickly when placed in a liter of water at room temperature?
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Q: The active transport of ions across the membrane causes an electrical gradient to build up across the plasma membrane.

A:
The active transport of ions across the membrane causes an electrical gradient to build up across the what?
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