单项选择题

According to the passage, how did knowledge about chemical processes increase before the seventeenth century

A．Philosophers devised theories about chemical properties.
B．A special symbolic language was developed.
C．Experience led workers to revise their techniques.
D．Experts shared their discoveries with the public.
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单项选择题
Which of the following statements best explains why the second of these was the more serious impediment
A．Chemical knowledge was limited to a small number of people.
B．The symbolic language used was very imprecise.
C．Very few new discoveries were made by alchemists.
D．The records of the chemical processes were not based on experiments.
单项选择题
When the writer says that if we expect others to mistreat us we are seldom disappointed, he means _______.
A．we are seldom disappointed because others mistreat us
B．we are seldom disappointed because others doesn’t mistreat us
C．it is easy for us to mistrust others
D．others are forced to mistreat us
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