哪位人物较早提出以太是不存在的观点：（）
参考答案：恩斯特-马赫
The secretary worked late into night, _____ a long speech for the president. [ ]
A. to prepare
B. preparing
C. prepared
D. was preparing
“纵使我满腹爱情，而爱情的真谛是清醒。”句中的“纵使”起到怎样的表达效果？
答：_______________________________________________________
