Directions: Read the passage below and select the best word choices to complete the passage.

Cloze Passage

A series of experiments performed by scientists from UK and Japan __1__ that coffee and naps __2__ together maximize the brain’s alertness much better than when taken alone.
Scientists at Loughborough University in Britain found out that tired test takers who drank a cup of coffee and immediately took a __3__ nap had __4__ than those who only drank coffee or only took a nap.

The secret is in how the combination of caffeine and sleep __5__ a neuromodulator called adenosine.

Normal activity slowly raises the level of adenosine in the brain, __6__ makes us __7__. Coffee reduces adenosine, while sleep naturally clears it from the brain.

As research shows that it takes __8__ affecting the brain, taking a nap immediately after drinking coffee enhances its effect on adenosine.

Scientists say __9__ should drink coffee quickly in order to have enough time for the nap, __10__ no more than 20 minutes. For those who do not fall asleep easily, scientists say even a half-asleep stage works.