Which figure has been packed with unit cubes correctly? a A rectangular prism that is packed with unit cubes in four rows, four columns, and one layer. There are three cubes missing. b A rectangular prism that is packed with unit cubes in two rows, three columns, and two layers. There is one cube missing from each layer. c A rectangular prism that is packed with unit cubes in four rows, two columns, and three layers. There are no cubes missing. d A rectangular prism that is packed with unit cubes in three rows, two columns, and four layers. There are three cubes missing from the top layer and one cube missing from the second layer