A.conquered B.crossing C.embarrass D.fooling E.hugely F.independent G.licensed H.jye.ai I.subconsciously J.tripping K.typical

What makes a problem "hard"？
There is a saying in the filed of artificial intelligence： "Hard things are easy；easy things are hard." Activities that most people find very hard，such as playing chess or doing highest mathematics，have given way fairly readily to computation，yet many tasks that humans find easy or even trivial resist being （1）

A

A

by machines.
   Twenty-five years ago Garry Kasparov became the first chess grand master to lose to computer.Today computer programs can beat the world's best players at poker and Go，what music and even pass the famous Turing test （2）

D

D

people into thinking they are talking another human.Yet computers still struggle to do things most of us human beings find easy，what can （3）

C

C

even the most advanced machines，such as learning to speak our native tongue or predicting from body language whether a pedestrian is about to cross the street - something that human drivers do （4）

I

I

.
   AI researchers will tell you that chess turned out to be comparatively easy because it follows （5）

H

H

rules that create a finite number of possible plays.Predicting the intentions of a pedestrian，however，is a more complex and fluid task that is had to reduce to rules.No doubt that is true，but I think there is a bigger lesson in the AI experience that applies to more urgent problems.Let's call it the vaccine-vaccination paradox.
   Anyone familiar with biology is （6）

E

E

impressed by the scientific work that in under a year yielded astonishingly effective vaccines to fight COVID-19.Yet even several months after the vaccines were （7）

G

G

for use，it is extremely hard to get all the countries fully vaccinated，especially in some part of the western world.The hard task of creating a vaccine proved relatively easy；the easy task of vaccination has proved very hard.
   Maybe it is time to rethink our categories.We call the physical sciences "hard" because they deal with issues that are mostly（8）

F

F

of the changes of human nature；they often laws that （at least in the right circumstances） yield exact answers.But physics and chemistry will never tell us how to design an effective vaccination program or solve the problem of the（9）

B

B

pedestrian，in part because they do not help us comprehend human behavior.The social sciences rarely yield exact answers.But that does not make them easy.When it comes to solving real-life problems，it is the supposedly straightforward ones that seem to be（10）

J

J

us.The vaccine-vaccination paradox suggests that the truly hard sciences are those that involve human behavior.