However, after-class activities can take up a lot of time, _____ students have to learn how to organ

However, after-class activities can take up a lot of time, _____ students have to learn how to organize their busy schedule.
A. and B. so C. 不填 D. but
【答案】B
【解析】
【详解】考查连词。句意：然而，课外活动会占用很多时间，所以学生必须学会如何安排他们繁忙的日程。根据句意可知，前后句之间为因果关系，所以用连词so连接。故选B。