According to Paragraph 6, what error had Ames made at first？
A. He thought only man-made chemicals dangerous.
B. He suspected his experiments and tests.
C. He is sometimes naive and ignorant.
D. He considered most natural substances negative.
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The word barbarians in Paragraph 9 is closest in meaning to______.
A. impolite people
B. wild animals
C. wasteland
D. uncivilized people
题图所示RLC串联的正弦电路，当ω=5000rad/s时发生谐振，已知R=5Ω，L=100mH，端口总电压有效值U=10mV。求Q和通带宽度BW值及电路所标变量的有效值。
题图所示交流电路，当ω=1000rad/s时发生谐振，已知端口总电压有效值U=180V。求电容C值及端口电流有效值I。
Based on the passage, which of the following statements can best describe the side effects
About 5 to 10 percent of children experience mild temporary side effects.
B. Side effects of a flu vaccine will usually last for a very long period of time.
C. If a child has never been infected by flu, he or she is more likely to have side effects
D. If a person has been exposed to the influenza virus before, he or she will not have side effects
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