Some people are questioning the sincerity of her promises.一些人质疑她的诺言是否诚恳。

Her apology was spoken with sincerity.她的道歉很诚恳。

In all sincerity [=in all honesty], we could not have done this project without your help.十分坦诚地说，没有你的帮助我们无法完成这项工程。