阅读下面短文，从短文后各题所给的四个选项（A、B、C和D）中，选出可以填入的空白处的最佳选项，并从答题卡上将该选项涂黑。
You have waited 45 minutes for the valuable 10 minutes’ break between classes. But when the bell for the next class rings, you can’t   36   how quickly time has passed.
If you are familiar with this  37  , you’ll know how time flies when you are having fun-and  38   when you are bored. Now scientists have  39   a reason why this is the case.
Scans have shown that patterns of activity in the brain  40   according to how we focus on a task. When we are   41  , we concentrate more on how time is passing. And this makes our brains   42   the clock is ticking more slowly.
In an experiment   43   by a French laboratory, 12 volunteers watched an image   44   
researchers monitored their brain activity.
The volunteers were told to   45   concentrate on how long an image appeared for, then
 46   the color of the image, and thirdly, study both duration and color. The results showed that 47   was more active when the volunteers paid  48   subjects.
It is thought that if the brain is  49   focusing on many aspects of a task, it has to  50  its resources, and pays less attention to the clock.  51 , time passes without us really  52   it, and seems to go quickly. If the brain is not so active, it concentrates its  53   energies on monitoring the passing of time.  54  , time seems to drag.
Next time you feel bored  55  , perhaps you should pay more attention to what the teacher is saying!

A．guess B．learn C．believe D．doubt

A．view B．point C．scene D．experience

A．drags B．stops C．backs D．gains

A．thought over B．made up C．suggested D．come up with

A．change B．develop C．grow D．slow

A．sleepy B．bored C．excited D．active

A．report B．think C．decide D．see

A．produced B．carried C．tried D．performed

A．so B．when C．while D．but

A．partly B．quickly C．how D．first

A．remember B．focus on C．forget D．tell apart

A．the researchers B．the experiment C．the clock D．the brain

A．much attention to B．more attention to C．attention to many D．attention to more

A．busy B．likely C．ready D．sure

A．focus B．gather C．reach D．spread

A．However B．Furthermore C．Therefore D．Finally

A．recognizing B．watching C．noticing D．counting

A．enough B．full C．right D．proper

A．In fact B．As a result C．For example D．Instead

A．in class B．with work C．in mind D．of lessons