阅读理解

　　Before the mid-nineteenth century, people in the United States ate most foods only in season. Drying, smoking and salting could keep meat for a short time, but the chance of eating fresh meat and drinking fresh milk was very limited: there was no way to keep food from going bad. But in 1810 a French inventor named Nicolas Appert developed the cooking-and-sealing technique of canning. And in the 1850's, an American named Gail Borden developed a means of keeping milk fresh. Canned foods and condensed milk (炼乳) became more common during the 1860's, but supplies remained low because cans had to be made by hand. By 1880, however, inventors had developed modern machines that mass-produced cans from tin-plate. Suddenly all kinds of food could be kept and bought at all times of the year.

　　Other inventions had also helped make it possible for Americans to change their daily diets. Growing populations increased food demand, and stimulated fruit and vegetable farmers to raise more produce . Railroad refrigerator cars made it possible to ship growers and packed meat fresh to faraway places without worrying they would go bad. Thus, by the 1890's northern city settlers could enjoy southern and western strawberries, grapes, and tomatoes, for a month at most in the past, for up to six months of the year. Besides, increased use of iceboxes made it possible for families to store food which could easily go bad. An easy means of producing ice had been invented in the 1870's, and by 1900 the nation had more than two thousand ice plants, most of which made home deliveries. The icebox became common equipment in most homes and remained so until the refrigerator replaced it in the 1920 's and 1930's. Almost everyone now has a variety of diet.

1．What does the passage mainly discuss?

[　　]

A．Causes of food going bad.

B．Production of iceboxes.

C．Inventions that led to changes in food and drink.

D．Canned food.

2．The underlined word“stimulate” means ________.

[　　]

A．protect

B．encourage

C．enable

D．persuade

3．The writer suggested that in the 1920's and 1930's home deliveries of ice ________.

[　　]

A．reduced in number

B．became very common

C．increased in cost

D．took place all the year

4．Which of the following is supported by the passage?

[　　]

A．Cans and iceboxes helped develop food supply .

B．Ice factories were developed by railroad refrigerator cars.

C．Most farmers in the United States raised fruits and vegetables.

D．People demanded home deliveries of variety of food and drink.