It was in 2017 ______Donald Trump became president of the United States.
【正确答案】 A
【答案解析】去掉It was和空处后，句子结构依然完整，由此可判断，本句为强调句。强调句的基本结构为：It is／was+被强调部分+that／who+其他部分。本题强调的是时间状语in 2017。故选A。