问题 选择题

右图为人的胃部血液循环示意图,若A、B、C为对应血管中的血流速度,则下列血液流速关系式、表述正确的是

A. A>B=C     B.  A=C>B   C.  B>A>C    D. A>C>B

答案

答案:D

分析:血管分为动脉、静脉、毛细血管三种,动脉是将血液从心脏输送到身体个部分去的血管,静脉是把血液从身体各部分送回心脏的血管,毛细血管是连通于最小的动脉与静脉之间的血管.

解答:解:动脉是将血液从心脏输送到身体个部分去的血管,动脉的管壁厚、弹性大,管内血流速度快;静脉是把血液从身体各部分送回心脏的血管,静脉的管壁薄、弹性小、官腔大,管内血流速度慢;毛细血管是连通于最小的动脉与静脉之间的血管,毛细血管的管腔很细,只允许红细胞单行通过,血流速度最慢.根据以上特点可判定图示中的三种血管:C是静脉,A是动脉,B是毛细血管,其血液流速关系可表示为:A>C>B.

故选:D

点评:解答此题的关键是掌握三种血管的特点、血流速度和血流方向.

单项选择题
单项选择题

Beyond question, Clinton was supposed to close up, stay out of sight, and avoid second- guessing his wife’s boss. After his ego blustered into oncoming traffic during Hillary’s heated primary race (1) Obama, the nation suffered from yet another turn of Clinton fatigue.

(2) this week Bill Clinton showed an instinct for robust, inclusive leadership that the (3) White House occupant could make good use of right for the time being. With President Obama struggling to (4) the political damage from the Gulf oil spill, Clinton not only can’t help himself—he’s worth being listened.

The conventional-wisdom (5) on President Obama’s early reaction to the spill was (6) he didn’t emote enough. He didn’t feel the (7) of all those people in the crisis whose livelihood would be destroyed, whose clean waters and wildlife would be (8) in black gunk.

Clinton considers this is an unfair (9) but offers a different—and more pointed— lesson to his young successor. "I think we ought to (10) in the same boat for a while... Let’s just (11) the problem, and then we can hold everybody responsible and emote or not emote, " Clinton conversed (12) CNN Anchor Wolf Blitzer.

Obama’s first (13) after the oil spill was to "feel the blame" rather than "feel the pain, " which are pretty sarcastic words as it were. No one intends to let British Petroleum (BP) management (14) the hook—for dangerously cutting corners, and for a (15) safety record. However, the President’s (16) focus on scolding BP consumed (17) White House energy while the oil gushed.

Great leaders don’t rush to criticise; Instead they instinctively (18) solutions. Rudy Giuliani, who didn’t stop to blame (19) intelligence for letting it happen, stood out from New York mayor with a girlfriend problem to 9/11 hero when he took control of a crisis and instilled confidence that a ravaged city could (20) beyond a terrorist attack.

18()

A. call for

B. sum up

C. go over

D. look for