Which should be the correct answer for following question. If I consider Nexus I feel 'b' is correct choice.

During Sprints, a Development Team has to wait for another team to provide
some dependent input. Often this leads to delay in completing their work. What can be
recommended to this team?
a) The team is not cross functional enough. The team should take Scrum Master's
help in educating the organization to add team members with appropriate skills 
b) The team should agree on Service Level Agreement (SLA) with another team and
escalate to Scrum Master if the SLA breached