Canned goods and condensed milk became more common during the 1860's, but supplies remained low because cans had to be made by hand. By 1880, however, inventors had fashioned stamping and soldering machines that mass-produced cans from tinplate. Suddenly all kinds of food could be preserved and bought at all times of the year.
Other trends and inventions had also helped make it possible for Americans to vary their daily diet. Growing urban populations created demand that encouraged fruit and vegetable farmers to raise more produce. Railroad refrigerator cars enabled growers and meat packers to ship perishables great distances and to preserve them for longer periods. Thus, by the 1890's, northern city dwellers could enjoy southern and western strawberries, grapes, and tomatoes, previously available for a month at most, for up to six months of the year. In addition, increased use of iceboxes enabled families to store perishables. All easy means of producing ice commercially had been invented in the 1870's, and by 1900 the nation had more than two thousand commercial ice plants, most of which made home deliveries. The icebox became a fixture in most homes and remained so until the mechanized refrigerator replaced it in the 1920's and 1930's.
What does the passage mainly discuss?
A.Causes of food spoilage
B.Commercial production of ice
C.Inventions that led to changes in the American diet
D.Population movement in the nineteenth century
第1题
检索尚未确定的供应商的订单号,正确的语句是()。
A.SELECT * FROM 订购单 WHERE 供应商号 NULL
B.SELECT * FROM 订购单 WHERE 供应商号 =NULL
C.SELECT * FROM 订购单 WHERE 供应商号 IS NULL
D.SELECT * FROM 订购单 WHERE 供应商号 IS NOT NULL
第2题
检索尚未确定的供应商的订单号,正确的命令是()。
A.SELECT * FROM 订购单 WHERE 供应商号 NULL
B.SELECT * FROM 订购单 WHERE 供应商号 =NULL
C.SELECT * FROM 订购单 WHERE 供应商号 IS NULL
D.SELECT * FROM 订购单 WHERE 供应商号 IS NOT NULL
第3题
检索尚未确定的供应商的订单号,正确的命令是()。
A.SELECT*FROM 订购单 WHERE 供应商号 NULL
B.SELECT*FROM 订购单 WHERE 供应商号 =NULL
C.SELECT*FROM 订购单 WHERE 供应商号 IS NULL
D.SELECT*FROM 订购单 WHERE 供应商号 IS NOT NULL
第4题
检索尚未确定的供应商的定单号,正确的命令是
A.SELECT * FROM订购单WHERE供应商号NULL
B.SELECT * FROM订购单WHERE供应商号=NULL
C.SELECT * FROM订购单WHERE供应商号IS NULL
D.SELECT * FROM订购单WHERE供应商号IS NOT NULL
第5题
查询尚未最后确定订购单的有关信息的正确命令是()。
A.SELECT名称,联系人,电话号码,订单号FROM客户,订购单WHERE客户.订单号=订购单.订单号and订购日期IS NULL
B.SELECT名称,联系人,电话号码,订单号FROM客户,订购单WHERE客户.订单号=订购单.订单号and订购日期=NULL
C.SRLECT名称,联系人,电话号码,订单号FROM客户,订购单FOR客户.订单号=订购单.订单号and订购日期IS NULL
D.SELECT名称,联系人,电话号码,订单号FROM客户,订购单FOR客户.订单号=订购单.订单号and订购日期=NULL
第6题
查询尚未最后确定订购单的有关信息的正确命令是()。
A.SELECT名称,联系人,电话号码,订单号FROM客户,订购单WHERE客户.客户号=订购单.客户号AND订购日期IS NULL
B.SELECT名称,联系人,电话号码,订单号FROM客户,订购单WHERE客户.客户号=订购单.客户号AND订购日期=NULL
C.SELECT名称,联系人,电话号码,订单号FROM客户,订购单FOR客户.客户号=订购单.客户号AND订购日期IS NULL
D.SELECT名称,联系人,电话号码,订单号FROM客户,订购单FOR客户.客户号=订购单.客户号AND订购日期=NULL
第7题
查询尚未最后确定订购单的有关信息的正确命令是()。
A.SELECT名称,联系人,电话号码,订单号FROM客户,订购单WHERE客户.客户号=订购单.客户号AND订购日期IS NULL
B.SELECT名称,联系人,电话号码,订单号FROM客户,订购单WHERE客户.客户号=订购单.客户号AND订购日期=NULL
C.SELECT名称,联系人,电话号码,订单号FROM客户,订购单FOR客户.客户号=订购单.客户号AND订购日期IS NULL
D.SELECT名称,联系人,电话号码,订单号FROM客户,订购单FOR客户.客户号=订购单.客户号AND订购日期=NULL
第8题
客户(客户号,名称,联系人,地址,电话号码) 产品(产品号,名称,规格说明,单价) 订购单(订单号,客户号,产品号,数量,订购日期) 查询尚未最后确定订购单的有关信息的正确命令是()。
A.SELECT名称,联系人,电话号码,订单号FROM客户,订购单WHERE客户.客户号=订购单.客户号AND订购日期IS NULL
B.SELECT名称,联系人,电话号码,订单号FROM客户,订购单WHERE客户.客户号=订购单.客户号AND订购日期=NULL
C.SELECT名称,联系人,电话号码,订单号FROM客户,订购单FOR客户.客户号=订购单.客户号 AND订购日期IS NULL
D.SELECT名称,联系人,电话号码,订单号FROM客户,订购单FOR客户.客户号=订购单.客户号 AND订购日期=NULL
第9题
(33 )查询尚未最后确定订购单的有关信息的正确命令是
A ) SELECT 名称 , 联系人 , 电话号码 , 订单号 FROM 客户 , 订购单
WHERE 客户 . 客户号 = 订购单 . 客户号 AND 订购日期 IS NULL
B ) SELECT 名称 , 联系人 , 电话号码 , 订单号 FROM 客户 , 订购单
WHERE 客户 . 客户号 = 订购单 . 客户号 AND 订购日期 =NULL
C ) SELECT 名称 , 联系人 , 电话号码 , 订单号 FROM 客户 , 订购单
FOR 客户 . 客户号 = 订购单 . 客户号 AND 订购日期 IS NULL
D ) SELECT 名称 , 联系人 , 电话号码 , 订单号 FROM 客户 , 订购单
FOR 客户 . 客户号 = 订购 单 . 客户号 AND 订购日期 =NULL
第10题
A.SELECT名称,联系人,电话号码,订单号FROM客户,订购单 WHERE客户.客户号=订购单.客户号AND订购日期IS NULL
B.SELECT名称,联系人,电话号码,订单号FROM客户,订购单 WHERE客户.客户号=订购单.客户号AND订购日期=NULL
C.SELECT名称,联系人,电话号码,订单号FROM客户,订购单 FOR客户.客户号=订购单.客户号AND订购日期IS NULL
D.SELECT名称,联系人,电话号码,订单号FROM客户,订购单 FOR客户.客户号=订购单.客户号AND订购日期=NULL
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