<em>Worthwhile . </em>This is the correct option.
Worthwhile means: useful, valuable, effective and significant. The Pony Express, which was a sort of mailing service (XIX) that connected the West and the East in the U.S during the mid 1800's, was very useful and valuabe for the author. This mailing service was carried out by horses which were run by different riders. The horse riders stopped at different points and were replaced by other riders. This sytem was faster than sending mail by ship or coaches. It was also significant because the system was so effective that Lincoln's inagural speech (1861) reached California in a very short time. Therefore, the author thinks that the <em>Pony Express</em> was effectively organized ; men and horses were used to make the coasts be connected and the effort was valuable because it must have given origin to the organization of the means of communication in the U.S.
These options are not right:
-History ( This refers to a field of study. It does not refer to an opinion. The <em>Pony Express</em> is part of the U.S History).
-Monument ( This is a noun. The writer labels the <em>Pony Express</em> with this word. There is not an opinion in the word).
-Physical ( This is an adjective that shows the type of work that was needed. This work was physical. The description is objective. It is not reflecting the author's opinion).
I think its should Be "Never Talk to strangers, Nor,get in a stangers car" Just my opinion
