单选题
Not until the early years of the 19th century ______what heat is.
A. man did know B. man know
C. didn't man know D. did man know
【正确答案】
D
【答案解析】[解析] 看到Not until．．．的句型，可知此为倒装句，只有C和D符合。改写为正常语序为：Man did not know what heat is until the early years of the l9th．现在将not提前，后面就不能再用否定，否则意思就变了。