可持续发展能力不断增强，经济结构调整取得显著成效，人口总量得到有效控制，生态环境明显

下列哪一种药物最不易引起神经损害而致聋

A．链霉素
B．卡那霉素
C．新霉素
D．庆大霉素
E．先锋霉素

屋面防水等级为Ⅲ级的工程是指( )。

A．特别重要的民用建筑和对防水有特殊要求的工业建筑
B．重要的工业与民用建筑、高层建筑
C．一般的工业与民用建筑
D．非永久性的建筑

金刚石和石墨的物理性质不同，是由于（　　）

A．组成两种物质的元素不同

B．两种物质碳原子个数不同

C．两种物质中碳原子的排列方式不同

D．构成两种物质的碳原子不同

测定运动员体能的一种装置如图所示，运动员质量为m₁，绳拴在腰间沿水平方向跨过滑轮（不计滑轮质量及摩擦），下悬一个质量为m₂的重物，人用力蹬传送带而人的重心不动，使传送带以速率v匀速向右运动．下面是人对传送带做功的四种说法，其中正确的是（　　）

A．人对传送带不做功

B．人对传送带做负功

C．人对传送带做功的功率为m₂gv

D．人对传送带做功的功率为（m₁+m₂）gv

The day was star-crossed: Friday the 13th in the month of October, on the eve of the second looming anniversary of a devastating market crash. "I’m telling you, psychology is really funny. People get crazy in situations like that," said portfolio strategist Elaine Garzarelli. Last week Friday the 13th lived up to its frightful reputation. After drifting lower at a sleepy pace for most of the day, the Dow Jones industrial average abruptly lurched into a hair-raising sky dive in the final hour of trading.

The Bush Administration moved swiftly to avert any sense of crisis after the market closed. Declared Treasury Secretary Nicholas Brady: "It’s important to recognize that today’s stock market decline doesn’t signal any fundamental change in the condition of the economy. The economy remains well balanced, and the outlook is for continued moderate growth." But Massachusetts Democrat Edward Markey, who chairs a House subcommittee on telecommunications and finance, vowed to hold hearings this week on the stock market slide. Said he: "This is the second heart attack. My hope is that before we have the inevitable third heart attack, we pay attention to these problems."

Experts found no shortage of culprits to blame for the latest shipwreck. A series of downbeat realizations converged on Friday, ranging from signs of a new burst of inflation to sagging corporate profits to troubles in the junk-bond market that has fueled major takeovers. The singular event that shook investors was the faltering of a $6.75 billion labor management buyout of UAL, the parent company of United Airlines, the second largest U. S. carrier.

On one point most thoughtful Wall Streeters agreed: the market had reached such dizzying heights that a correction of some sort seemed almost inevitable. Propelled by favorable economic news and a wave of multibillion-dollar takeovers, stocks had soared more than 1,000 points since the 1987 crash. But by last August some Wall streeters were clearly worried.

The heaviest blow to the market came Friday afternoon. In a three-paragraph statement, UAL said a labor-management group headed by Chairman Stephen Wolf had failed to get enough financing to acquire United. Several banks had apparently balked at the deal, which was to be partly financed through junk bonds. The take-over group said it would submit a revised bid "in the near term,’ but the announcement stunned investors who had come to view the United deal as the latest sure thing in the 1980s buyout binge. Said John Downey, a trader at the Chicago Board Options Exchange: "The airline stocks have looked like attractive takeover targets. But with the United deal in trouble, everyone started to wonder what other deals might not go through.

The tone of the writer as reflected in the first sentence is（）

A. sensible

B. irrational

C. defiant

D. ironical