题干
.
It was _____ his mother came in _____ to prepare his lessons.
It was _____ his mother came in _____ to prepare his lessons.
A：not until; did the boy begi
B：until; that the boy didn’t begi
C：until; did the boy not begi
D：not until; that the boy bega
答案(点此获取答案解析）
D
，一分子该物质与两分子溴发生加成反应的产物（不考虑顺反异构）理论上最多有