单项选择题

It can be inferred that "iodine, fluoride, calcium..." (Line 3, Para. 2) means _________.

A．substances which influence human health
B．harmful substances in the water supply
C．substances which help provide breeding places for pests
D．substances contributory to the height and strength of a person

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单项选择题

According to the passage, research into the influence of geography and climate should _________.

A．focus on unknown aspects
B．be pursued on a larger scale
C．be carried out among remote tribes
D．go ahead in depth

单项选择题

What does the passage mainly discus

A．The difference between general history, and art history.
B．What we can learn from art history.
C．The superiority of art history to general history.
D．The influence of artists over history.