热泵产品需要用电吗？
参考答案：
一定要用电，压缩机用电能来压缩制热，不是直接加热，空气源热泵还有风扇，也需要用电，但用电量较少。
患者女性，50岁，咬硬物致右上第二磨牙正中劈裂。拔牙前X线片显示患牙无龋及牙周病，根尖无阴影，上颌窦低位，腭根与上颌窦底重叠。术中腭根折断约2mm。
拔除上第二磨牙需麻醉的神经是（）
A.腭前神经和上牙槽后神经
B.腭前神经和上牙槽中神经
C.鼻腭神经和上牙槽前神经
D.鼻腭神经和上牙槽中神经
E.鼻腭神经和上牙槽后神经
Which of the following statements about price elasticity is most likely FALSE（）
A. The elasticity of demand of a good increases over time.
B. If the price of gasoline increases, total expenditures on gasoline will increase.
C. If the price of a brand of toilet paper increases, total expenditure on that brand of toilet paper will increase.
