题干
It was not until the 18th century that man realized that the whole of the brain was involved in the working of the mind， ？
A：was it
B：wasn’t it
C：did they
D：didn’t they
答案(点此获取答案解析）
A
”表示两种物质在一定条件下可相互转变．依据给出的信息推断并回答下列问题：