不定式2种独立用法
一、独立结构
to be frank
to be honest
to tell the truth
这三个词组是同义词，意思是“说实话”、“老实说”或“坦率地说”
To tell the truth， I am not happy at the moment.
二、与疑问词连用：不定式与疑问词who，which， when， how， what 等连用，在句中起名词作用，可充当主语、表语、宾语等。
He didn’t know what to say.(宾语)
How to solve the problem is very important.(主语)
My question is when to start. (表语)
在英语中，动词不定式可用作独立成分来修饰整个句子，常见的有：
to be honest (to be brief/exact/frank)
to begin with
to tell the truth
so to speak
to make a long story short
to say the least（至少可以这么说）
to say nothing of（姑且不说）
如:
— You’re in pretty lousy mood， huh?
— To say the least.
I have a point there， to say the least.
To make a long story short ， he is in hospital now.
To begin with， on behalf of all of your American guests， I wish to thank you for the incomparable hospitality.
