They have . . . . . . . . up the deficit.

The other options are incorrect because they do not mean the same thing as “cover.”

• To fill something means to put something inside it so that it is full. In this case, the people have not put anything inside the deficit, so they have not filled it.
• To make something means to create it. In this case, the people have not created the deficit, so they have not made it.
• To pull something means to move it towards you. In this case, the people have not moved the deficit towards them, so they have not pulled it.