it is + adj.+of/for sb.+to +doing?to是介词吗?介词后加doing?

it is + adj.+of/for sb.+to +doing?to是介词吗?介词后加doing?
it is + adj.+of/for sb.+to +doing?to是介词吗?介词后加doing?

it is + adj.+of/for sb.+to +doing?to是介词吗?介词后加doing?
不是,是不定式的标志.介词加动词的ing

应该是 it is + adj.+of/for sb.+to +do
to 在这里不是介词。介词后是需要加doing的

doing,动名词，具有名词和动词性质，动词性质是可有宾语和状语，组成动名词短语；名词性质就不说了，这里的就是做介词“to”的宾语