语境填空
【小题1】Tanis wrote this letter in order to show how________(感激的) she was to the center.
【小题2】However，it is also hard to keep a code book secret for long. So codes must be changed________(频繁的)．
【小题3】First，I will tell them the________(不利) of playing computer games and cheating in the exams.
【小题4】I________(真诚地) wish you a pleasant time with us.
【小题5】She herself lived a simple or rather poor life but she was so________(慷慨的) to the people in need of help.