内毒素的主要成份为（）
A 、肽聚糖
B 、蛋白质
C 、鞭毛
D 、核酸
E 、脂多糖
参考答案：E
I was about to give up my effort to work on the puzzle when a good idea _____ me. [ ]
A. beat
B. struck
C. attacked
D. caught
蓄电池机车在使用中，放电终止后不得低于每只蓄电池端电压（）伏。
A、1.75
B、1.6
C、1.9
about to give up my effort to work on the puzzle when a good idea _____ me. [ ]