In each set of sentences, choose the sentence that has a problem with pronoun-antecedent agreement. Students sometimes discover they don't like their chosen field.
A student sometimes discovers he or she doesn't like their chosen field.
Students may lose interest in their chosen field.

The sentence in this set of sentences that has a problem with the pronoun-antecedent agreement is:

A student sometimes discovers he or she doesn't like their chosen field.

Explanation:

The pronouns are "he or she" and "their."  These pronouns are preceded by the noun "student."  A better construction of the sentence is the first one, which says: "Students sometimes discover they don't like their chosen field."  The third sentence is also well-constructed.  They are simpler and less complicated than the second sentence.  Again, the first sentence has perfect agreement between the noun "students" and the pronouns "they" and "their."

ich statement best shows a problem in travels with charley?

one sharp difficulty presented itself. in the intervening twenty-five years my name had become reasonably well known.

this being so, my trip demanded that i leave my name and my identity at home.

i had to go alone and i had to be self-contained, a kind of casual turtle carrying his house on his back.

with all this in mind i wrote to the head office of a great corporation which manufactures trucks.