赞题库-背景图

单项选择题

一般来说，煤气和电力的需求交叉弹性系数（）。

A．大于零
B．小于零
C．等于0
D．无法判断

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热门试题

单项选择题What is indicated about replacement parts

A．They are not eligible for a discount
B．They are covered under the original warranty
C．They should be installed by a licensed professional
D．They must be returned within seven days for a full refund.

单项选择题What is true about the document

A．It was issued by the manufacturer
B．It does not have an expiration date
C．It is valid in more than one country
D．It does not apply to machine upgrades