What is the main reason the pony express was a quick way to deliver mail?

Although it wasn't nearly as quick as trains when they were invented ,the pony express took a shorter time to mail letters  than ships,which would often take many months,but anyways the main reason it was fast was because at a certain point the first mailman could stop to take a rest while another would step in and go further and this would go on,and since horses have been known to be fast it was rather easier to travel.

Explanation:

answer; i believe that the correct answer is culture based resources;

jupiter is mainly composed of hydrogen and helium just like a star. spectral analysis of jupiter has revealed that in addition to hydrogen and helium, the planet is made of water, methane and ammonia. those elements are in trace amounts. the core of the planet is thought to contain some rock and metallic hydrogen. i hope this will give you the answer to your question! : d