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

Example Input: Just as salty taste involves perception of sodium ions in saliva, sweet taste correlates with presence of glucose.
Example Output: Just as salty taste involves perception of sodium ions in saliva, what taste correlates with presence of glucose?

Example Input: The active transport of ions across the membrane causes an electrical gradient to build up across the plasma membrane.
Example Output: The active transport of ions across the membrane causes an electrical gradient to build up across the what?

Example Input: In the tropics tradewinds are the prevailing winds called.
Example Output:
In the tropics what are the prevailing winds called?