Clouds that form in flat layers are called?

Which of the following is not am example of a polymer? protein nylon kevlar concreta

The brightest star in the night sky in the northern hemisphere is sirius. its distance from earth is estimated to be 8.7 light years. a light year is the distance light travels in one year. light travels at a speed of 3.00 × 108 m/s. calculate the distance from earth to sirius in miles. (1 mi = 5280 ft) g

Is a volume of space that is empty of matter.