Who should make sure everyone on the Development Team does their tasks for the Sprint?

According to the Scrum Guide1, the Developers are self-organizing and decide how to turn Product Backlog items into an Increment of value. No one tells them how to do their work. The Developers are accountable for creating a plan for the Sprint, the Sprint Backlog. The other roles are not responsible for making sure everyone on the Development Team does their tasks for the Sprint.

References: Scrum Guide