Ethan has to push with more force on table A than on table B because of option d: Table A has more mass than table B.
The greater mass of table A would mean it has more inertia, making it harder to move. According to Newton's first law of motion, an object at rest will stay at rest unless acted upon by a net external force. Therefore, a table with more mass requires a greater force to initiate movement compared to a table with less mass.