[单选题]It's no secret that most of us don't get enough sleep and suffer for it.If you're between the ages of 16 and 64,1 don't get seven to nine hours ofsleep per night,your logical 2,executive function,attention,and mood can be impaired.3,severe sleep deprivation can lead to depression,anxiety,and 4 ofparanoia（妄想症）.In the long run,sleep deprivation is a main 5 to the nsk ofdementia and Alzheimer's disease.6,one group that doesn't need to heed these warnings i.s executives.In our 7 of 35,000 leaders and interviews with 250 more,we found that the more seruor a person's 8 is,the more sleep they get.There are tw0 9 explanations for this.Either senior executives,with the help of_10 and hard-working middle managers,do less and take more time for sleep.Or senior executives have had the 11 and discipline throughout their career to get enough sleep and 12 maintain a high performance level without 13.Our conclusion is that the latter is the 14."Sleep has always been foundational for my performance,"Cees't Hart,president and CEO of Carlsberg Group,shared with us."And 15 to perform in a way that is required by my current job,I need seven hours of sleep,every night.Of course,with 16 travel and work commitments,sometimes this is 17,and when that happens,it comes with a cost.When I sleep less,I perform less."18,our data found that 68%ofnon-executive leaders get five to seven hours of sleep per night.When there are not enough hours in the day,they 19 some from the night.Many leaders stay up late to catch up on email or other tasks.According to our research,this tendency is widespread,20 gender.13选？
A.burning out
B.breaking up
C.hanging over
D.holding back