Which is the MOST important reason why blog post title length matters?

Which is the MOST important reason why blog post title length matters?
  A)  Titles under 200 characters in length have the best click-through rate.
  B)  The length of your blog post doesn’t matter as long as it’s enticing.
  C)  You want your full title to be seen on a search engine results page to help with the click-through rate.
  D)  If the title is too long it will be cut off on social media.