What do a prism, a magnifying glass, a microscope, and eyeglasses all have in common? a) they are opaque. b) they refract light. c) they reflect light. d) they are translucent.

By definition, when the speed of the light changes when it passes from a material to another, this is called "Refraction of light". This happens when there is a difference in the index of refraction between both mediums o materials. Therefore, that speed depends of the medium through  it passes. 
 
 The index of refraction is expressed as below: 
 n=c/v
 
 "n"  is the index of refraction.
 "c" is is the speed of light.
 "v" is the phase velocity of light in the medium.
 
 A prism, a magnifying glass, a microscope, and eyeglasses refract light. Therefore, the correct option is: B) They refract light.