Answer:
Johan Sebastian Bach was a famous German composer form the period of Baroque. He was a member of famous family that gave us a large number of famous musician. He is mostly known and famous for his church and instrumental music, among which the most famous ones are <em><u>The Mass in B Minor and Brandenburg Concertos. H</u></em>is opus includes more than 1 000 different pieces. Hiss sons, Wilhelm, Carl Phillip and Johan Christian continued his path.
Explanation:
It is interesting that Bach was orphan since the age of 10, and was raised by a brother. He was a magnificent organist, and has worked across whole Germany, including Weimar, Leipzig and Kothen. He is been celebrated by Protestant church, for the achievement he made in the field of church music.
The apparent brightness is defined by how much light we get pretty much. The formula is:

This takes into account that the light is spreading out to a sphere that has the surface given by 4πd^2.
We have that d=20 ly and 1 ly is 9.46*10^12 km or 9.46*10^15m.
Hence, d=20*9.46*10^15=189.2 *10^15 m
Now, we can substitute the d value and calculate that L=<span>8.45184*

W/m^2</span>
Answer: b. Clear-cutting
Explanation: Clear cutting is a cheap and effective way of harvesting trees or timbers, this methods helps the forest operators to get the best out of a forest at a very reduced cost.
Clear-cutting is bad because removing the whole tree from an area destroys outrightly the natural habitat of most widelife, and it will also lead to the destruction of the eco-system that relies on the forest.