在正常情况下，有少量的凝血因子或促凝物质被激活或进入血液循环，血液不会发生凝固的最主要原因是（）

A.机体存在完整的抗凝系统，它与凝血系统保持动态平衡

B.血液中抗凝物质增多

C.血管壁的完整性

D.纤溶激活物增多

E.神经体液的调节作用

Selection to participate in a top executive-education program is an important rung on the ladder to top corporate jobs. U. S. corporations (1) billions of dollars in this form of management development -- and use it to (2) and train fast-track managers. Yet one (3) of executive education found that less than 5% of the managers (4) to these high-profile programs are women -- and minorities are terribly (5) as well.

The numbers are (6) . In regular business (7) usually paid for by the participant, not an employer -- there are plenty of women and minorities. Women, for example, (8) for about 30% of MBA candidates. Yet in the (9) programs paid for by corporations that round out a manager’s credentials at a (10) career point, usually at age 40 or 45, companies are making only a (11) investment in developing female and minority executives. A case (12) point: Only about 30% of the 180 executives in Stanford’s recent (13) management program were women.

Most companies say these days they are (14) hiring and promoting women and minorities-- and there are some (15) trends in overall employment and pay levels so why are companies (16) the ball when it (17) executive education The schools (18) that they are neither the cause of nor the cure for the problem. A Harvard Business School dean figures that companies are (19) of sending their female executives (20) they don’t want to lose them to competitors.

8（）

A.occupy

B.possess

C.account

D.take