B

阅读下列短文，根据短文内容填空。在未给提示词的空白处仅填写1个恰当的单词，在给出提示词的空白处用括号内所给词的正确形式填空。

Why do humans prefer some smells over others? One theory, increasingly ____14____  (support) by experts, suggests that smell preferences are learned.It’s easy to explain how we determine ____15____ smells are dangerous or not: we learn. This has been adopted to ensure easier detection of gas leaks. Gas naturally ____16____ (have) no recognisable smell. However, a strong smell is added so that we can raise the alarm when we detect the smell associated with danger.

14.  _____

15._____   

16. _____