The answer is A. It twirls like a helix and has 2 strands
Dominate animals hunt the smaller and weaker animals for survival.
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