I'm looking for a short science fiction story about the Earth being invaded by aliens. The aliens are very intelligent and the human race is challenged to a debate with the aliens -- if the humans win the debate they live, and if the humans lose the debate, they are annihilated.
Surprisingly the humans chose not the smartest human to represent them but rather an ordinary little girl. She faces off with her alien opponent for the debate... she doesn't utter a single word... all she does is cry. The aliens unanimously decide that the humans win the debate and their freedom.
I was reading whatever anthologies of short stories I could find in my local library during the late 1960's and 1970's. This is a very moving story and I would appreciate everyone's help in identifying it so I can read this terrific story once again.
It may have appeared in one of the ORBIT series of anthologies edited by Damon Knight, or another series during that timeframe.