下列为恶性肿瘤的是（）。 A.多形性腺瘤 B.甲状腺囊腺瘤 C.成肌纤维细胞（肌纤维

一束光线垂直射到镜面上，则入射角是           ，反射角是       。

如图所示，有两根和水平方向成α角的光滑平行的金属轨道，上端接有可变电阻R，下端足够长，空间有垂直于轨道平面的匀强磁场，磁感强度为B，一根质量为m的金属杆从轨道上由静止滑下．经过足够长的时间，金属杆的速度趋近于一个最大速度v_m，则（　　）

A．如果B增大，v_m将变大

B．如果α变大，v_m将变大

C．如果R变小，v_m将变大

D．如果m变小，v_m将变大

原发性高血压病的主要病理生理是（）

A.心排出量升高

B.交感神经兴奋性增加

C.周围血管阻力增加

D.肾素分泌过多

E.血管内皮细胞过多分泌内皮素

"In the long run," as John Maynard Keynes observed, "we are all dead. " True. But can the (1) run be elongated in a way that makes the long run (2) And if so, how, and at what cost People have dreamt of (3) since time immemorial. They have sought it since the first alchemist put an elixir of (4) on the same shopping list as a way to turn lead into gold. They have (5) about it in fiction, from Rider Haggard’s "She" to Frank Herbert’s "Dune". And now, with the growth of (6) knowledge that has marked the past few decades, a few researchers believe it might be within (7) .

To think about the question, it is important to understand why organisms-people (8) -age in the first place. People are like machines: they (9) That much is obvious. However, a machine can always be (10) A good mechanic with a stock of spare parts can keep it going (11) . Eventually, no part of the (12) may remain, but it still carries on, like Lincoln’s famous axe that had three new handles and two new blade.

The question, of course, is whether the machine is worth (13) . It is here that people and nature (14) . Or, to put it slightly (15) , two bits of nature disagree with each other. From the individual’s point of view, (16) is an imperative. You cannot reproduce unless you are alive. A fear of death is a sensible evolved response and, since (17) is a sure way of dying, it is no surprise that people want to stop it in its tracks. Moreover, even the appearance of ageing can be (18) . It (19) the range of potential sexual partners who find you attractive-since it is a sign that you are not going to be (20) all that long to help bring up baby-and thus, again, curbs your reproduction.

18（）

A.useful

B.cheerful

C.harmful

D.doubtful

下述哪项不是血管外溶血（）

A.丙酮酸激酶缺陷症

B.先天性球形红细胞增多症

C.微血管病性溶血性贫血

D.不稳定血红蛋白病

E.阵发性睡眠性血红蛋白尿