Do you know what 　　　 in the room at the moment?

A．they were doing

B．were they doing

C．they are doing

D．are they doing

读取二进制文件的函数调用形式为：fread(buffer, size, count, pf);，其中buffer代表的是______。

A) 一个文件指针，指向待读取的文件
B) 一个整型变量，代表待读取的数据的字节数
C) 一个内存块的首地址，代表读入数据存放的地址
D) 一个内存块的字节数