判断题讲座的结尾有固定的模式，需要对整个讲座做一个归纳。A 对B 错

第一步，本题考查容斥原理，用公式法解题。
第二步，设没有报名参加其中任何一场讲座的有x人。根据三集合非标准型容斥原理公式，可列方程42＋51＋88－30－2×12＝139－x，解得x＝12。（或者使用尾数法解题）

由题干易知该中学举办的两类讲座，一年级学生都有参加。故C项一定为真。其余选项都不必然为真，均不选。

LECTURE NOTICE?March 12,2010
Dear Neighborhoods,
Nowadays,the crime among teenagers seems increasing,so we invite a famous professor,Dr．Li Zhigang from Beijing Normal University to give a lecture on the topic“Teenagers'Education at Home”．This lecture could be very helpful to us who are doubt in how to communicate with our own children,who feel difficult to control our children,who don't know how to deal with the problems our children face and so on．We will have personal discussion with the professor after the lecture if you need any help from him．
The lecture will begin at 8:00 p．m．Friday,in the Meeting Room,Building 4．One member,at least from each family,is required to attend．
Please be there on time．If you have any problem to be present,please call 54312789．
Neighborhoods'Committee