instruction:
You are given a sentence and your task is to generate another sentence that supports the given input.
question:
An example of this type of crystal is sodium chloride (NaCl).
answer:
Compounds like sodium chloride form structures called crystals.


question:
Mass on a Vertical Spring When simple harmonic motion is discussed in introductory textbooks, the mass connected to the spring usually slides on a frictionless horizontal surface.
answer:
An object attached to a spring sliding on a frictionless surface is an uncomplicated type of simple harmonic oscillator.


question:
Human actions have caused the extinction of hundreds of species of birds, and some 1,200 species  are threatened with extinction today.
answer:

Around 1200 species of birds are currently at risk of extinction due to human activity.