Why are open questions the most important questions to use in social work practice?

Why are open questions the most important questions to use in social work practice?
 
  a. They encourage others to describe what they are concerned about in depth
  and serve as a kind of open invitation for clients to say whatever they may
  want to discuss, which promotes exploration, and can be empowering as well
  b. They express your confusion about what clients are saying to you
  c. They are used to direct your client toward a particular topic or answer
  d. They allow clients to drift off focus, giving you an opportunity to challenge
  their engagement in work