[13] "With the immediate carbon emission reduction benefit from replacing fossil-based non-renewable concrete and steel with renewable mass timber products, the urgent climate change crisis can be mitigated now to help save our future." Which main idea does Hongmei Gu's point help to develop? It is imperative that we stop using fossil-based non-renewable concrete right away. O B. There needs to be more research on how to produce renewable mass timber products. OA.