What is an astronomical unit or AU? A)

A unit of time equal to one light year or 6 trillion miles.

B)

A unit of distance equal to the average distance from Earth to the Suntor

93 million miles.

A unit of distance equal to the size of the Milky Way Galaxy or 100,000

light years across

D)

A unit of time that is equal to the amount of time it takes light to travel

from the Sun to Earth,

B

Explanation:

The correct option should be B.

The Astronomical Unit, AU, is a measurement unit for length in general astronomy and represents the mean or the average distance of the sun from the earth.

Mathematically, in astronomy,

1 astronomical unit = 150,000,000 km

But then, 1 km = 0.621371 mile

Hence,

150,000,000 km = 150,000,000 x 0.621371 miles

            ≈93,000,000 miles

Therefore, 1 astronomical unit can also said to be approximately equal to 93,000,000 miles.

The correct option is B

1. efficient use of space

2. elimination of groundwater contamination

3. energy generation

4. lower carbon footprint