Why is the Sales Qualified Lead (SQL) stage important for both your sales and marketing teams?

Why is the Sales Qualified Lead (SQL) stage important for both your sales and marketing teams?
  A)  It will help your sales and marketing teams remain on the same page in terms of the quality and volume of MQLs that marketing is handing over
  B)  It will help your marketing team better nurture Opportunities prior to sending them over to the sales team to be more thoroughly researched
  C)  It has no relevance to smarketing and is simply used for executive teams to track sales activity
  D)  There is no difference between an SQL and an MQL, thus this stage has no relevance to smarketing