Why do we say sitting is killing people?
A. The risk of dying for those sitting too much rises by 11 percent.
B. The death rate for those sitting too much is about 20 percent higher than for others.
C. The death rate for those sitting too much is about 40 percent higher than for others.
D. Those sitting too much are usually at a higher risk of dying.
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Why do health experts suggest people should stand up for health?
A. Because standing burns more calories.
Because standing provides muscle activity people need.
C. Because standing helps keep blood sugar under control.
D. All of the above.
What does the author want to tell us?
A. The harm of sitting too much.
B. How to keep healthy.
C. The relationship between sitting and standing.
D. Some habits are fatal.
X射线是德国物理学家（）发现的。
A. 库利吉
B. 居里夫人
C. 伦琴
D. 万莱沃纳
传统的X射线技术用的是透视原理。
A. 对
B. 错
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