e. The Development Team should have all the skills necessary to deliver the Done Increment
Cross-Functional Scrum Teams are the teams having all the necessary skills and proficiency within the team to accomplish their work. These teams do not rely on anyone outside the team for completing the work items.
Thus, the Scrum Team is a very creative amalgamation of different skills required to complete the entire work item. Each team member may not necessarily have all the skills required to build the product but is competent in his/her area of expertise.
Having said that, the team member need not be cross-functional but the team as a whole has to be.