The given line "A time when overland travel was slow and cumbersome" best illustrates the "physical endurance" required for the Pony Express
Answer: Option A
Explanation:
Between Missouri and California, a mail service was use to take place for delivering mails, newspaper and message from 1860 to 1861 with the help of horse –mounted riders and this service termed as “Pony Express”.
The physical endurance required for it is a time when overland travel was slow and cumbersome as during those times the communication and transportation sources were very rare and hectic due to lack of knowledge, inventions and development which now resulted into a boon therefore communicating is no more a big deal as before.
