讨论] 大全968， 为什么对等的时间状语，用的时态不一样？

cathy0929

968.        Interest rates on mortgages have declined steadily during the first six months of this year but virtually remained unchanged during the next three months.

(A) have declined steadily during the first six months of this year but virtually remained unchanged

(B) declined steadily during the first six months of this year but virtually remain unchanged

(C) steadily declined during the first six months of this year but remain virtually unchanged

(D) declined steadily during the first six months of this but have remained virtually unchanging’（E）

(E) declined steadily during the first six months of this year but have remained virtually unchanged

 

答案选E，我选的是B，前半句的时间状语是 during the first six months of this year，
            后半句的时间状语是during the next three months，那么时态应该是很清楚的，一般过去时和一般现在时，为什么后半句是现在完成时，对现在有影响吗？
            

 

另外这一句的virtually的位置我也不是太明白，是不是virtually在remained前和后都可以啊？

 

谢谢大家的解释