问题
选择题
Not until the early years of the 19th century ___ know what heat is. [ ]
A. man did
B. man
C. didn't man
D. did man
答案
答案:D
Not until the early years of the 19th century ___ know what heat is. [ ]
A. man did
B. man
C. didn't man
D. did man
答案:D