[单选题]压电晶片的振动频率即探头的（）。
A.工作频率
B.重复频率
C.扫查频率
D.固有频率

[多项选择]某单位100名职工按工资额分为3000元以下、3000～4000元、4000～6000元、6000～8000元、8000元以上等5个组。这一分组（）。
A. 是等距分组
B. 分组标志是连续型变量
C. 末组组中值为8000元
D. 相邻的组限是重叠的
E. 某职工工资6000元，应计在6000～8000元组内

[单选题]从20世纪70年代开始，经济学家就已经发现，经济增长并不必然带来满意度。总体说，有钱人比穷人幸福，一个贫民窟的穷人突然变成中产了，他会非常幸福；但在达到一定水平之后，金钱对幸福的影响程度会越来越小。因为当一个人的收入增加时，他们对于“多少收入才算幸福”的期望值也在同步增加。而且，一个人越是看重钱在个人幸福中的作用，就越不满意，因为这时相对收入比绝对收入更重要，永远有比你更有钱的人。作者通过文段想要告诉读者的是( )。
A.穷人比富人更能感受到幸福
B.人们对于金钱的欲望是无法满足的
C.金钱并不一定能使人长久幸福
D.总体上看有钱人比穷人更幸福

[单选题]某患者患慢性支气管炎30余年，慢性阻塞性肺疾病10余年，当该患者在稳定时可知道在家中进行长期家庭氧疗，护士健康教育时，应告诉患者不属于治疗有效表现的是（）。
A.血压下降
B.发绀减轻
C.呼吸频率减慢
D.气急减轻
E.心率减慢

[单项选择]

Sparks created in a lab give off X-rays, scientists announced Monday.
X-rays are a byproduct (副产物) of high-energy electron discharges in the Sun, in exploding stars, and even in lightning. Many scientists did not expect sparks alone to do the trick.
Researchers at Florida Institute of Technology brought their equipment, which had detected X-rays in lightning, into the lab. Half the team expected to see X-rays and the other half did not.
In sparks of 1.5 million to 2 million volts, the researchers indeed recorded X-rays that were remarkably similar to those produced by lightning.
"This amazed us, It opens the door to answering really big questions about lightning by generating it in the lab," said team member Hamid Rassoul. "It also tells us that we have a lot’ to learn about how even small sparks work."
X-rays are a form of electromagnetic radiation, on a spectrum (频谱) that runs from radio waves on the low
A. Scientists Created X-rays in a Lab.
B. Sparks, a New Way to Produce X-rays.
C. Runaway Breakdown Triggers New Questions.
D. Scientists Surprised by X-rays from Lab Lightning.