OFFICIAL EXPLANATION
For one to insure one's home can be costly, and amount to a sum of $1500 per year.A. one's home can be costly, and amount to a sum of
Not quite.
This answer choice is grammatically correct but stylistically flawed because it is overly wordy. There is another answer choice that expresses the same meaning in fewer words.B. his home can be costly, and amount to
Incorrect.
This answer choice is grammatically incorrect. The pronoun his can refer to human male nouns, but there's no such noun in the sentence.
What helps us identify this question as a Pronoun question as well as identify the mistake is the following Stop Sign:
Every pronoun in the underlined part of the sentence or after it
C. one's home can be costly, the amount sometimes even reaching
Not really.
This answer choice is grammatically correct but stylistically flawed because the phrase sometimes even reaching makes it overly wordy. There is another answer choice that expresses the same meaning in fewer words.D. their home can be costly, and amount to
Not quite.
Although this answer choice is less wordy than the original, it is grammatically incorrect: the pronoun their refers to one but does not agree with it as one is singular and their is plural.E. one's home can be costly, and amount to
This answer choice corrects the stylistic flaw in the original sentence. Using both amount to and a sum makes the sentence overly wordy. Additionally, it follows the pronoun rule: the pronoun one agrees with itself only.