An important lecture______ tomorrow, the professor has to stay up late into the night to prepare for it.
【正确答案】 A
【答案解析】逗号前后分句缺乏连词，且主语与谓语均不一致，因此前半句应采取独立主格结构，构成句子的原因状语，相当于As an important lecture will be given tomorrow，故A为正确答案。D为过去分词作后置定语，不符合语境。