The correct answer is C) draining swamps.
The action that did not create more farmland in Japan is draining swamps.
The main problem for agriculture in Japan is its short land and the rugged terrain. The rugged terrain in Japan is difficult for agriculture. Japan needs to import most of its fruits and vegetables and that is why they are expensive in Japan.
To help farmers in a region full of mountains, they had to carved terraces to into hillsides. Japanese is primarily a fish consumer market. They are surrounded by sea and fishing is the most important source of food.