A-A+
We may infer that iodine fluoride and calciu
问题详情
We may infer that "iodine, fluoride and calcium" are______.
A．substances which act positively or negatively on man"s health
B．harmful substances in the water supply
C．substances which help provide breeding places for pests
D．substances contributory to good health
参考答案
正确答案：A
解析：该题检查上下文的理解。从第二段"enjoy exceptionally good or had health，scientists have identified contributory factors such as the presence or absence of substances like...”，我们可确定[A]为本题答案。
