问题
单项选择题 A1/A2型题
对减慢窦性心动过速最佳的药物是（）
A.洋地黄
B.维拉帕米
C.阿替洛尔
D.胺碘酮
E.苯妥英钠
答案
参考答案：B
解析：其能抑制窦房结及房室交界区的自律性，延长房室结传导，使心率减慢。
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对减慢窦性心动过速最佳的药物是（）
A.洋地黄
B.维拉帕米
C.阿替洛尔
D.胺碘酮
E.苯妥英钠
参考答案：B
解析：其能抑制窦房结及房室交界区的自律性，延长房室结传导，使心率减慢。
Passage Three
| For centuries, explorers have risked their lives venturing into the unknown for reasons that were to varying degrees economic and nationalistic (国家主义的). Columbus went west to look for better trade routes to the Orient and to promote the greater glory of Spain. Lewis and Clark journeyed into the American wilderness to find out what the U. S. had acquired when it purchased Louisiana, and the Appolo astronauts rocketed to the moon in a dramatic show of technological muscle during the cold war. Although their missions blended commercial and political military imperatives, the explorers involved all accomplished some significant science simply by going where no scientists had gone before. Today Mars looms (隐约出现) as humanity’s next great terra incognita (未探明之地). And with growing emphasis on international cooperation in large space ventures, it is clear that imperatives (需要，必要) other than profits or nationalism will have to compel human beings to leave their tracks on the planet’s reddish surface. Could it be that science, which has long played a minor role in exploration, is at last destined to take a leading role The question naturally invites a couple of others: Are there experiments that only humans could do on Mars Could those experiments provide insights profound enough to justify the expense of sending people across inter- planetary space With Mars the scientific stakes are arguably higher than they have ever been. The issue of whether life ever existed on the planet, and whether it persists to this day, has been highlighted by mounting evidence that the Red Planet once had abundant stable, liquid water and by the continuing controversy over suggestions that bacterial fossils rode to Earth on a meteorite (陨石) from Mars. A more conclusive answer about life on Mars, past or present, would give researchers invaluable data about the range of conditions under which a planet can generate the complex chemistry that leads to life. If it could be established that life arose independently on Mars and Earth, the finding would provide the first concrete clues in one of the deepest mysteries in all of science: the prevalence of life in the universe. |
What is the main goal of sending human missions to Mars
A．To find out if life ever existed there.
B．To see if humans could survive there.
C．To prove the feasibility of large-scale space ventures.
D．To show the leading role of science in space exploration.