1979年WH0将冠心病分为（） A.无症状性心肌缺血 B.缺血性心肌病 C.心绞痛

如图甲所示，表面绝缘、倾角θ=30°的斜面固定在水平地面上，斜面所在空间有一宽度D=0.40m的匀强磁场区域，其边界与斜面底边平行，磁场方向垂直斜面向上．一个质量m=0.10kg、总电阻R=0.25W的单匝矩形金属框abcd，放在斜面的底端，其中ab边与斜面底边重合，ab边长L=0.50m．从t=0时刻开始，线框在垂直cd边沿斜面向上大小恒定的拉力作用下，从静止开始运动，当线框的ab边离开磁场区域时撤去拉力，线框继续向上运动，线框向上运动过程中速度与时间的关系如图乙所示．已知线框在整个运动过程中始终未脱离斜面，且保持ab边与斜面底边平行，线框与斜面之间的动摩擦因数，重力加速度g取10 m/s²．求：

（1）线框受到的拉力F的大小；

（2）匀强磁场的磁感应强度B的大小；

（3）线框在斜面上运动的过程中产生的焦耳热Q．

GB50174-2008《电子信息系统机房设计规范》规定：电子信息系统机房的耐火等级不应低于几级（）。

A.一级；

B.二级；

C.三级。

春秋战国时期的成语故事与故事中的主人公对应有误的一项是( )。

A．立木取信——商鞅

B．卧薪尝胆——勾践

C．围魏救赵——孙武

D．图穷匕见——荆轲

某建设项目以财务净现值为指标进行敏感性分析的有关数据见下表，则该建设项目投资额变化幅度的临界点是( )。

A．+8.13%
B．+10.54%
C．+12.31%
D．+16.37%

It’s no surprise that Jennifer Senior’s insightful, provocative magazine cover story, “I love My Children, I Hate My Life,” is arousing much chatter–nothing gets people talking like the suggestion that child rearing is anything less than a completely fulfilling, life-enriching experience. Rather than concluding that children make parents either happy or miserable, Senior suggests we need to redefine happiness: instead of thinking of it as something that can be measured by moment-to-moment joy, we should consider being happy as a past-tense condition. Even though the day-to-day experience of raising kids can be soul-crushingly hard, Senior writes that “the very things that in the moment dampen our moods can later be sources of intense gratification and delight.”
The magazine cover showing an attractive mother holding a cute baby is hardly the only Madonna-and-child image on newsstands this week. There are also stories about newly adoptive–and newly single–mom Sandra Bullock, as well as the usual “Jennifer Aniston is pregnant” news. Practically every week features at least one celebrity mom, or mom-to-be, smiling on the newsstands.
In a society that so persistently celebrates procreation, is it any wonder that admitting you regret having children is equivalent to admitting you support kitten-killing It doesn’t seem quite fair, then, to compare the regrets of parents to the regrets of the children. Unhappy parents rarely are provoked to wonder if they shouldn’t have had kids, but unhappy childless folks are bothered with the message that children are the single most important thing in the world: obviously their misery must be a direct result of the gaping baby-size holes in their lives.
Of course, the image of parenthood that celebrity magazines like Us Weekly and People present is hugely unrealistic, especially when the parents are single mothers like Bullock. According to several studies concluding that parents are less happy than childless couples, single parents are the least happy of all. No shock there, considering how much work it is to raise a kid without a partner to lean on; yet to hear Sandra and Britney tell it, raising a kid on their “own” (read: with round-the-clock help) is a piece of cake.
It’s hard to imagine that many people are dumb enough to want children just because Reese and Angelina make it look so glamorous: most adults understand that a baby is not a haircut. But it’s interesting to wonder if the images we see every week of stress-free, happiness-enhancing parenthood aren’t in some small, subconscious way contributing to our own dissatisfactions with the actual experience, in the same way that a small part of us hoped getting “ the Rachel” might make us look just a little bit like Jennifer Aniston.

We learn from Paragraph 2 that

A．celebrity moms are a permanent source for gossip.
B．single mothers with babies deserve greater attention.
C．news about pregnant celebrities is entertaining.
D．having children is highly valued by the public.