下列叙述正确的是（ ） A．-4100是无理数 B．(2-3)+(3-2)是有理数C

“三八二十三，人人说我憨，我的卖完了，你的往回担。”这首打油诗说的是一个精明的小商贩在街上卖韭菜，按一斤八分，二斤一毛六，三斤二毛三的价格收钱的现象。就这一分的让利，使他的生意每天都特别好。该小商贩的精明做法给我们的启示是，做生意应该 [ ]

①不断降低商品价格

②善于运用经营策略

③懂得价格影响供求的道理

④千方百计提高产品质量

A．①②

B．①④

C．②③

D．①③

一个人在竖直放置的平面镜前以1m/s的速度向后离开镜面，则像相对镜面的速度的大小是（　　）

A．0.5m/s

B．1m/s

C．2m/s

D．4m/s

学校管理学是研究学校内部管理活动现象及其规律的一门学科，是（）交叉而成的一门边缘科学。

A.教育科学

B.规律科学

C.自然科学

D.管理科学

电话会议室内噪音应（）dB。

A.≤40

B.≤20

C.≤30

D.≤25

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.

13（）

A.research

B.instinct

C.plan

D.strategy