sth.is sth.,and is sth.和 sth.is sth.,and it is sth.哪个正确?（sth

Sth is done sth by sb such is sth that... it is possible to do sth和it possible to do sth谁是正确的 It is possible for sb(sth) to do sth it is my frist time to do sth / or doing sth/or do sth? It is time to do sth和It is time for sth有区别吗? is he do/dong sth? sb.is up to sth. she is sth.with sb. 可以说It is easy doing sth吗 it is difficult doing.sth造句 it is n.to do sth.