In the early 20th century, the automobile companies of Ransom E.

In the early 20th century, the automobile companies of Ransom E. Olds and Henry Ford popularized ______.
【正确答案】：the assembly line
【题目解析】：In the early 20th century, the automobile companies of Ransom E. Olds and Henry Ford popularized the assembly line. 参见教材P234。