Answer the following question given this paragraph: 

Some comets have periods of thousands or even millions of years. Most long-period comets come from a very distant region of the solar system. This region is called the Oort cloud. The Oort cloud is about 50,000–100,000 times the distance from the Sun to Earth.


Q: What is the name of the cloud where most long-period comets come from?


A:
oort cloud