单选题 You should have attended that lecture on durability testing of fibers; it really was most ______.

【正确答案】 B

【答案解析】[考点] 词义辨析
[解析] irrelevant：不相干的；stimulating：使人振奋的；sensitive：敏感的，体贴的；secure：牢固的，安心的，根据句意选B。