truthfully       
adverb uk/ˈtruːθ.fəl.i/ us/ˈtruːθ.fəl.i/
 诚实地;讲真话地;真实地,如实地
in a way that is honest and does not contain or tell any lies
  I answered her questions truthfully. 我如实回答了她的问题。 
 I can truthfully say I never heard my parents shouting. 老实说,我从未听过我父母大喊大叫。 
 See: truthful
 - More examples
 - You were right to speak truthfully to the police.
 - Truthfully, I did find it hard to settle down.
 - You should respond as truthfully as possible.