input: Text: BIG ANCESTOR By F. L. WALLACE Illustrated by EMSH Man's family tree was awesome enough to give every galactic race an inferiority complex—but then he tried to climb it! In repose, Taphetta the Ribboneer resembled a fancy giant bow on a package. His four flat legs looped out and in, the ends tucked under his wide, thin body, which constituted the knot at the middle. His neck was flat, too, arching out in another loop. Of all his features, only his head had appreciable thickness and it was crowned with a dozen long though narrower ribbons. Taphetta rattled the head fronds together in a surprisingly good imitation of speech. "Yes, I've heard the legend." "It's more than a legend," said Sam Halden, biologist. The reaction was not unexpected—non-humans tended to dismiss the data as convenient speculation and nothing more. "There are at least a hundred kinds of humans, each supposedly originating in strict seclusion on as many widely scattered planets. Obviously there was no contact throughout the ages before space travel— and yet each planetary race can interbreed with a minimum of ten others! That's more than a legend—one hell of a lot more!" "It is impressive," admitted Taphetta. "But I find it mildly distasteful to consider mating with someone who does not belong to my species." "That's because you're unique," said Halden. "Outside of your own world, there's nothing like
  Question: What is both a gift and curse of humanity?
  
   (A) They are intellectually superior, but unable to mate with other species (and therefore grow their population) due to galactic mating laws
   (B) They are biologically superior, but their restrictive mating abilities prevent them from growing their population as fast as other species
   (C) They have a tendency to unify against a potential threat, but are unaware of how they could overtake other species through strength in unification
   (D) They have a tendency to fall in love easily, which is difficult to manage when they become attracted to 'higher-level'  species, who are off limits
  Answer:
output: They have a tendency to unify against a potential threat, but are unaware of how they could overtake other species through strength in unification