According to the text, there are four facts that support the thesis:
A) Japan considered raw materials to be important: according to the text raw materials were essencial for the Japan's imports.
C) Japan depended on imports to obtain iron: the steel industry relied on iron for functioning so Japan had to import iron.
D) Japan ensured the security of trade routes: Japan had to focus on the security of the trade routes to guaratee that the supply chain would not be affected.
E) Japan located major sources of iron in China: Manchuria and northern China were the main sources of imported iron for Japan.