填空题

Suppose we built a robot to explore the planet Mars. We provide the robot with seeing detectors to keep it away from danger. It is powered entirely by the sun. Should we program the robot to be 1 active at all times No. The robot would be using up energy at a time when it was not receiving any. So we would probably program it to 2 its activity at night and to wake up at dawn the next morning.
According to the evolutionary (进行的) theory of sleep, evolution equipped us with a 3 pattern of sleeping and waking for the same reason. The theory does not deny that sleep provides some important 4 functions. It merely says that evolution has programmed us to perform those functions at a time when activity would be 5 and possibly dangerous. However, sleep protects us only from the sort of trouble we might walk into; it does not protect us from trouble that comes looking for us. So we sleep well when we are in a familiar, safe place, but we sleep 6 when we fear that bears will nose into the tent.
The evolutionary theory 7 well for differences in sleep among creatures. Why do cats, for instance, sleep so much, while horses sleep so little Cats can afford to have long periods of 8 because they spend little time eating and are unlikely to be attacked while they sleep. Horses must spend almost all their waking hours eating because their food is very low in 9 Moreover, they cannot afford to sleep too long or too deeply because their 10 depends on their ability to run away from attackers.
A. accounts I. cancel
B. survival J. lightly
C. inefficient K. particularly
D. inactivity L. restorative
E. widely M. equally
F. cease N. affects
G. regular O. extensive
H. energy