单项选择题

The title that best expresses the ideas of the passage is （）

A．"Why are there shadows"
B．"The transparent materials"
C．"How to cast a shadow"
D．"Shadows and light waves"

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热门试题

单项选择题An opaque material is （）

A．a material that can be seen through
B．a translucent(半透明的) material
C．a material that can not be seen through
D．a lucent material

单项选择题Which of the following is not true（）

A．Light waves are beams of light.
B．Light waves can penetrate any materials except men' s bodies.
C．Light waves can penetrate transparent materials.
D．Light waves can penetrate some materials.