41.   Researchers have long known that potassium can reduce blood pressure, and some small studies had suggested that increasing its consumption could help prevent strokes.

42.   Researchers have long known that unripe fruits, whose seeds are not yet fully developed, could contain foul-tasting chemicals that prevented animals from plucking them prematurely.

43.   Researchers know that heat and moisture in the atmosphere can distort radio signals.

44.   Researchers know there are differences between the light and dark forms of the peppered moths besides their wing coloration.

45.   Researchers long have known that diabetes occurs much more often in Hispanic Americans than in whites or blacks.

46.   Researchers now know that the disorder is biological and often runs in families.

47.   Researchers do not know why the fungal disease is emerging now.

48.   Researchers do not know, but they believe that a kind of cell called a stem cell would be easiest to work with.

49.   Researchers have known for some time that mice genetically engineered to lack the receptor for serotonin, a neurotransmitter, show anxiety-like behavior.

50.   Researchers have known from the virtual outset of the program that Head Start had no effect at all on IQ scores.