Not until the early years of the 19th ce
题型:选择题
问题:
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
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