Having taken our seats, ______.

A．the professor began the lecture

B．the lecture began in no time

C．we were attracted by the lecture immediately

D．the bell announced the beginning of the lecture

Having taken our seats,_______________________.

________, the professor began the lecture.

A．Seen that we had taken our seats         B．Having taken our seats

C．When we took our seats                            D．Seating ourselves well