Do you wake up every day feeling too tired, or even upset If so, then a new alarm clock could be just for you.The clock, called SleepSmart, measures your sleep cycle, and waits (1) you to be in your lightest phase of sleep (2) rousing you. Its makers say that should (3) you wake up feeling refreshed every morning.As you sleep you pass (4) a sequence of sleep states—light sleep, deep sleep and REM(rapid eye movement) sleep—that (5)f approximately every 90 minutes. The point in that cycle at which you wake can (6) how you feel later, and may (7) have a greater impact than how much or little you have slept. Being roused during a light phase (8) you are more likely to wake up energetic.SleepSmart (9) the distinct pattern of brain waves (10) during each phase of sleep, via a headband equipped (11) electrodes (电极)and a microprocessor. This measures the electrical activity of the wearer’s brain, in much the (12) way as some machines used for medical and research (13) , and communicates wirelessly with a clock unit near the bed. You (14) the clock with the latest time at (15) you want to be wakened, and it (16) duly(适时地)wakes you during the last light sleep phase before that.The (17) was invented by a group of students at Brown University in Rhode Island (18) a friend complained of waking up tired and performing poorly on a test. " (19) sleep-deprived people ourselves, we started thinking of (20) to do about it," says Eric Shashoua, a recent college graduate and now chief executive officer of Axon Sleep Research Laboratories, a company created by the students to develop their idea. 14().

A. prompt
B. program
C. plug
D. plan