Today' s teenagers seem to be more liberal in their ideas than their _______ grandparents.
A. freethinking B. traditional C. old D. happy
Klebold and Harris felt _______ and wanted to revenge against those who disliked playing
together with them or laughed at them.
A. discouraged B. ashamed C. tired D. separated
根据下文的disliked playing together with them判断此处应为"感到孤立"，故选D。