Given a scientific passage and an answer, generate a question for the given answer.

Passage: Resistance is the property that determines the amount of current flow through a particular material. Answer: resistance
What is the property that determines the amount of current flow through a particular material?

Passage: Nobody really has such colorful eyes! The colors were added digitally after the photo was taken. They represent all the different colors of light. Light is a form of energy that travels in waves. Light of different colors has different wavelengths. Answer: wavelengths
Different colors of light differ in terms of which important attribute?

Passage: The organs of the GI tract are lined with mucous membranes that secrete digestive enzymes and absorb nutrients. The organs are also covered by layers of muscle that enable peristalsis. Peristalsis is an involuntary muscle contraction that moves rapidly along an organ like a wave (see Figure below ). You can watch an animation of peristalsis at this link: http://en. wikipedia. org/wiki/File:Peristalsis. gif . Answer: peristalsis
What is an involuntary muscle contraction that moves rapidly along an organ like a wave called?