■当两个带 to 不定式由 and 或 or 连接时，第二个不定式符号常可省略。例如：

I intend to call on him and discuss this question again.

Christina hardly knew whether to laugh or cry.

She asked me to telephone or wire to her on Monday.

■若两个并列的‍带不定式有对比含义，第二个不定式符号便不能省略。例如：

To be or not to be, that is the question. 存在还是毁灭，是个要考虑的问题。

I haven't decided to go home or to stay at school this summer .

■不用并列连词的情况下，第二个不定式符号也不能省略。例如：

Please go to the seaside to swim, to get suntanned.

He likes to stay with the peasants, to work in the fields with them.

■当三个或三个以上带不定式构成排比结构时，所有的不定式符号均须保留。例如：

Read not to contradict or confute; nor to believe and take for granted; not to find talk and discourse; but to weigh and consider.

（以上摘自《新编高级英语语法》，章振邦主编，上海外语教育出版社2012年12月第1版）

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