有一道填空

These years, the rate of interest always __fluctuates between 4% and 6%_( 在4%和6%之间浮动 )
fluctuate:vi.
变动, 波动, 涨落, 上下, 动摇

fluctuates between 4 percent and 6 percent

fluctuates between 4 percent and 6 percent
在两者之间应该用between...and...的吧

楼上的不错

fluctuated between 4% and 6%
these years 主要是对这些年做评论或分析，所以用过去式