You get a rat and you put it in a cage, and you give it two water bottles: One is just water, and the other is water laced with either heroin or cocaine.
ネズミを手に入れてオリに入れ ２本の水ボトルを設置します 一つは水だけ もう一つは 水にヘロインかコカインを混ぜたもの