It happened do 和to do 有什么区别?

happened to do和‘happen to do ;区别? it +形容词+to do sth 和it is +形容词+to do sth 有什么区别? it's +比较级+to do sth和it +形容词+to do sth有什么区别 think it hard to do 和 i think it's hard to do 有什么区别 It happened to be 和There happened to be有什么区别? what to do和how to do it有什么区别? begin to do和start to do有什么区别 Trying to do和try to do 有什么区别? try to do和manage to do 有什么区别 It's +adj of sb to do sth 和 It's for sb to do sth有什么区别? it's a time to do sth 和it's time to do sth 有什么区别 It is adj for sb to do和It is adj of sb to do有什么区别