Question

it is a waste of time doing还是to do为什么

Answer 1

是

It is a waste of time to do something.

因为这是动词不定式的复合结构。 

It's adj. for sb to do sth for sb to do sth是真正的主语，sb是to do sth的逻辑主语的。

如： It is impossible for him to get up early. It's important (for me) to carry on practicing speaking for learning English. 

动词不定式的复合结构是“for / of sb. to do sth.”。

扩展资料

不定式复合结构的介词用for还是of,主要决定于前面形容词的性质。

一般说来,of前面的形容词是careful, clever, foolish, good, kind, nice, wise等,说明人的特性。

for前面的形容词是dangerous, difficult, easy, hard, heavy, important, interesting, necessary等,一般说明不定式动作的特性.

前面如果是名词用for。如:

1.It’s a good idea for parents to allow children to study in groups during the evening.

对父母来说,在晚上让孩子分组学习是个好主意。

2.It’s wise of him to do it well.

对他来说,把这件事做好很明智。

Answer 2

传统的用法为
It's a waste of time doing sth
It is a waste of time going to the doctor with most mild complaints.
一点小毛病就去看医生是浪费时间。
来自柯林斯例句
2. It is a waste of time warning him — he is determined to go his own way. 警告他等于浪费时间,因为他决心要照自己的意思去做. 来自《简明英汉词典》
但现在在非正式的英语中也有to do 的
It is a waste of time to read such a magazine. 看这种杂志真是浪费时间. 来自互联网
5. It is a waste of time to try to rehabilitate some criminals. 改造有些犯罪分子是浪费时间. 来自互联网

Answer 3

doing，为什么不知道老师讲的

Answer 4

to~~~~~~~