Flow-line operation: Refers to the working process and the sequence of action on the labor object to complete a certain amount of work in the production process, so that the production of the frontier without interruption. According to the definition above, which of the following is options? ['0 people in the shoemaking workshop, each person is responsible for a process, and finally produces a finished product.', 'Chinese college entrance examination revised paper, 15 teachers are responsible for the correction of a question type.', 'My son does his homework in the evening, then his math, and finally his English.', 'Purchase of raw materials-processing and production-finished products-sales.']