2000年，世界海洋经济占世界GDP总值230000亿美元的4%，其中主要海洋国家海洋产值分别占这些国家国内生产总值的（）左右。

A block and tackle is “rove to advantage”. This means that the（）.

A.blocks have been overhauled

B.hauling parts of two tackles are attached

C.hauling part leads through the movable block

D.hauling part leads through the standing block