求问it代词的指代问题【Japan received huge sums of capital from the Uni

求问it代词的指代问题
【Japan received huge sums of capital from the United States after the Second
World War,using it to help build】 amodern industrial system.
【划线部分】
A) Japan received huge sums of capital from the United States after the
Second World War,using it to help build
B) Japan received huge sums of capital from the United States after the
Second World War and used it to help in building
C) Japan used the huge sums of capital it received from the United States
after the Second World War to help build
D) Japan’s huge sums of capital received from the United States after the
Second World War were used to help it in building
答案说A选项的ing分词短语中的it 语法上指代了 the United States ,从哪里看出来呢?
A选项简化是Japan received huge sums of capital,(japan)use it to help?