单选题 By ______ a cheaper material for the steel in our products, we can greatly reduce manufacturing costs.
A. substituting B. replacing
C. alternating D. displacing

【正确答案】 A
【答案解析】[解析] 句子表示“用更便宜的材料代替钢铁”，意为“用A代替B”的词组substitute A for B放在空格处的句意最自然，故选A。