One of the most elusive pieces of green energy projects in the US isn't raw materials, labor, or even money.

在美国，绿色能源项目最难以捉摸的部分之一不是原材料、劳动力，甚至不是资金。

Sea fighting was rare because of the materials, labor, and preparation needed to succeed.

海战很少见，因为成功需要材料、劳动力和准备工作。