单项选择题

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
<上一题 目录 下一题>
热门 试题

单项选择题
The author mentions Samuel Butler and other English writers' tales because______.
A．they teach logic to the readers
B．they show a sense of satire
C．they proved that machines can reproduce themselves
D．they described the imaginary future world of machines
单项选择题
Which of the following may be the best title of this passage
A．The Importance of Geographical Environment.
B．The Influence of Geographical Environment on Man.
C．Generalization of Types of People.
D．Geographical Environment, a Mysterious Subject.
相关试题