单项选择题According to the passage, the demand for recyclable materials in the manufacturing of new products is sometimes sluggish because ______.
单项选择题It can be concluded from the passage that the introduction of electronic media into the world of music ______.
单项选择题What is the author’s attitude towards animal research
单项选择题By advancing the theory of ______, Bacon showed the new empirical attitutes toward truth about nature and bravely challenged the medieval scholasticists.
单项选择题Why does America confront the mineral resources problems