题干
Over the past decades, sea ice in the Arctic as a result of global warming.
A：had decreased
B：decreased
C：has been decreasing
D：is decreasing
答案(点此获取答案解析）
C
)的合成路线如下:
(R、R´表示H或烃基)
+HI→ 
+CH3I
+NaI+H2O