在猪腹背部位，肌肉组织主要由（）、（）、（）、（）构成。

小明和妈妈到皮鞋批发站订购发价为100元的真皮皮鞋80双，妈妈对批发商说：“如果你肯降价，那么你每降1元，我就多订购4双．”批发商很快就同意了，原因是他经过计算的，若降价5%，则由于小明的妈妈多订购，获得的利润反而比原来多100元．小朋友，你知道这种皮鞋的成本是多少元吗？

已知|x|=3，|y|=2，且xy＜0，则x+y的值等于[ ]

A．5

B．1

C．±5

D．±1

人力资源最重要的指标，集中体现为员工个人的（）水平。

通过交谈或问卷的方法了解一些人对某一事件的感受、态度和行为，在医学心理学的研究方法中属于（）

A.调查法

B.临床观察法

C.个案法

D.实验法

E.心理测验法

The notion of NP-completeness has provided a (66) mathematical definition for (67) intractability of NP problems. But this measure applies only to worst-case complexity. Being NP-complete does not (68) that a problem is intractable on the average case. Indeed, some NP-complete problems are " (69) on average", though some may not be. Levin initiated the study of average-case intractability, He showed that a bounded tiling problem under a simple distribution is average-case NP-complete. Since then, several additional average-case NP-complete problems have been shown within Levin’s (70) . This paper is intended to provide a comprehensive survey of average-case NP-complete problems that have been published so far, and the techniques of obtaining these results.

（68）处填（）。

A．direct

B．navigate

C．indicate

D．show