The research is so designed that once _______ nothing can be done to change it.
A. begins
B. having begun
C. beginning
D. begun
答案：D
解析：由于 the research 与 begin 是被动关系，所以要用过去分词 begun。Once begun 可视为 once it is begun的省略。 https://t.cn/z8AXL9l

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#7个月大婴儿就任美国名誉市长#

#7个月大婴儿就任美国名誉市长#
【唯美英语】想你，是一种美丽的忧伤的甜蜜的惆怅，心里面，却是一种用任何语言也无法表达的温馨。
　　It is graceful grief and sweet sadness to think of you, but in my heart, there is a kind of soft warmth that can’t be expressed with any choice of words.