Analysis of test questions: this question is to examine the ability to obtain information from materials and interpret information. From the material "How to cherish acacia trees in steelmaking, an inch of acacia and an inch of steel". It reflects that the Great Leap Forward centered on iron and steel smelting led to a serious imbalance in the proportion of the national economy, and a large number of trees were cut down to destroy the ecological environment, so B meets the meaning of the question. So choose B.