B) Cuba's economy weakened
I would assume probably cholera, does not sound like my cup of tea anyway!
Camels made trade possible across the Sahara. Although there were no trade routes until the 7th and 8th centuries, Camels were use to the climates and weather conditions making it possible to ship goods and other products around without much trouble.
One reason for the increased twinning rates begin to be the increase in assistive reproductive technologies. Including fertility boosting medications, artificial insemination, vitro fertilization (IVF) is the most popular.