Over the past decades,sea ice ________ in the arctic as a result of global warming.
问题描述：
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
此题为什么选答案C,
答
根据sea ice海里的冰被减少了,可知使用被动,因此ABD都不对另外本句是过去对现在造成了影响因此要用现在完成时态被动+现在完成时因此答案选择C冰变少仍在进行，因此用被动+现在完成进行时 因此答案选择C