China began to open to the outside world in the late 1970s. , there have been great change

China began to open to the outside world in the late 1970s. , there have been great changes in the country.
A. By then
B. As a result
CAt last
D. In all

A. By then(答案→)B. As a resultC. At last D. In all解析：句意:在20世纪70年代后期，中国开始对外开放。结果中国发生了很大的变化。by then 到那时为止；as a result 结果是……； at last 最后；in all 总而言之。根据句意可知，对外开放的结果是让中国发生了巨大的变化。故选B。

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