1.He didn't answer the phone even though his phone has been ringing.
2.Even if it isn't the best way,it is the only way that can slove the problem.
3.The office telephone rang many times already,but nobody answered it.
4.It isn't that I don't want to open the door for you,but my mom doesn't allow it.
5.If i knew he was such a person,I won't take him to work here.