Origin of the phrase "the bee's knees"

[Rich7]

Test No. incompl/inter-81 "Save Our Animals (1)", question 7

But as far ......... Cathy was concerned, he was the bee's knees (someone to admire) and when she left school, she went to work as his assistant in the Society for the Protection of Animals.

(a) so
(b) more
(c) than
(d) as

Test No. incompl/inter-81 "Save Our Animals (1)", answer 7

But as far as Cathy was concerned, he was the bee's knees (someone to admire) and when she left school, she went to work as his assistant in the Society for the Protection of Animals.

Correct answer: (d) as

Your answer was: correct
_________________________

bee's knees?
you know the story or origin?

[Torsten]

Well Richard, what about you? You probably know that there are lots of possible explanations as to the origin of the phrase bee's knees.
It's said have appeared in North America during the 1920s. One of the theories is that bees carry pollen back to their hives in small sacs on their legs and that's why the concentrated goodness might be found around the bee's knees.

TOEFL listening lectures: A lecture from a science class