What enabled trade between han china and the roman empire other than the silk road?

The sea. They used the sea and the silk road to trade. 
Thanks
Hope this could help

Ican answer some, but not all! 2.) sensory info not being transmitted to the brian will result in a lack of responses that could be life saving. 4.) sensory adaption will helo people recognize certain images or objects that will give them a clearer understanding and expand their knowledge. them also become familiar with their surroundings. 8.) light the retina detect an object as it passes through the pupil and into the retina. 12.) cones in the retina us see color. they us see red. blue and green