the policeman could not swear to having seen the accused man at the scene of为什么是swear to having 而不是to have

问题描述:

the policeman could not swear to having seen the accused man at the scene of
为什么是swear to having 而不是to have

swear后面的to不是副词而是介词,合在一起表示这个警察不能够向某个事实发誓

“swear to sth.” 是一个固定的短语,意思是“断言,肯定,保证”
所以上句中having 是动名词,如果用have的话就错了,因为短语中to后不能加动词
要记住,to 是一个介词,它可以接动词,也可以接名词,虽然一般来说都是动词,但涉及到某些固定搭配,或者表示朝、向某种趋势等时,后面会加名词或动名词,例如:see to sth.办理,照管,料理