Which of the following substances,found in soil,is used by plants to make proteins.
问题描述：
Which of the following substances,found in soil,is used by plants to make proteins.
A Carbon dioxide
B Nitrate
C Oxygen
D Vitamins
答
B Nitrate
能够从土壤里找到的,肯定不是氧气和二氧化碳,维他命更不可能.
剩下的只有硝酸盐了.