Research on animal intelligence always makes me wonder just how smart humans are (1) _____ the fruit-fly experiments described in Carl Zimmer’s piece in the Science Times on Tuesday.Fruit flies who were taught to be smarter than the average fruit fly (2) _____ to live shorter lives.This suggests that (3) _____ bulbs bum longer, that there is an advantage in not being too terrifically bright.

　　Intelligence, it (4) _____, is a high-priced option.It takes more upkeep, bums more fuel and is slow off the starting line because it depends on learning—a gradual (5) _____ —instead of instinct.Plenty of other species are able to learn, and one of the things they’ve apparently learned is when to (6) _____.

　　Is there an adaptive value to (7) _____ intelligence? That’s the question behind this new research.I like it.Instead of casting a wistful glance (8) _____ at all the species we’ve left in the dust I.Q.-wise, it implicitly asks what the real (9) _____ of our own intelligence might be.This is on the mind of every animal I’ve ever met.

　　Research on animal intelligence also makes me wonder what experiments animals would (10) _____ on humans if they had the chance.Every cat with an owner, for instance, is running a small-scale study in operant conditioning; we believe that if animals ran the labs, they would test us to determine the limits of our patience, our faithfulness, our memory for terrain.
____

A.tended

B.feared

C.happened

D.threatened