There are many reasons to why slaves were essential in the colonial economy:
Slaves were generally used more in the south, because large plantations were found there, which meant that the need for large amounts of workers.
Slaves provided cheap labors, and as they were not "citizens" of the US, they were not allowed their rights.
Slaves were also relatively easy to buy and replace, however, their survival rates were not that good after they traveled long distance.
etc.
hope this helps
Galapagos islands are groups of island in the pacific ocean that are known to have a wide range of native animals such as giant tortoise that found no where else on earth. These native animals helped Darwin in the development of the theory of natural significance which attributes to the biological significance of the Galapagos islands. Human species is a threat to the natural wildlife on these islands mainly due to poaching and destruction of natural forests that destroys habitat and also impacts negatively on biological diversity of living organisms.
The answer is (B. Medium) because it has to travel through the ear drum evenly without busting it. Hope this helped :)