问题
单项选择题
铸造卡环的描述，不恰当的是
A．卡环臂起始部分宽厚，越向尖端越窄薄
B．卡环臂尖有固位、支持、稳定作用
C．卡环臂呈内扁外圆的半圆形
D．卡环体位于基牙非倒凹区
E．卡环尖位于基牙倒凹区
答案
参考答案：B
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铸造卡环的描述，不恰当的是
A．卡环臂起始部分宽厚，越向尖端越窄薄
B．卡环臂尖有固位、支持、稳定作用
C．卡环臂呈内扁外圆的半圆形
D．卡环体位于基牙非倒凹区
E．卡环尖位于基牙倒凹区
参考答案：B
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| New Energy in the Twenty-first Century Energy from the wind Wind is a kind of clean energy, and there is lots of it, but, if there's no wind, there is no wind energy. Energy from the water When water moves from a high place to a lower place, it can make electricity (电) without pollution. However, people have to build dams (水坝) to use this energy, and building dams is very expensive. Energy from the earth There is heat in the rocks under the earth. Scientists use the heat to make geothermal (地热的) energy. This kind of energy is cheap, but it is only possible in a few places in the world. Energy from the sun Solar panels (太阳电池板) on the roofs of houses can turn energy from the sun into electricity. Solar power is clean and plentiful (丰富的), but when the weather is bad. It doesn't work. | |||||||||||||||
New Energy in Twenty-first Century
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