Improve the bracketed part of the sentence by choosing the most appropriate option: "The priest agreed (to answer on) questions on theology."

Introduction / Context:
This sentence improvement question focuses on the correct verb and preposition pattern after the verb agreed. The sentence describes a priest who accepted a request to respond to questions on theology. The phrase to answer on is slightly awkward and must be improved to make the sentence grammatically correct and idiomatic.

Given Data / Assumptions:

- Original sentence: The priest agreed (to answer on) questions on theology. - Bracketed phrase: to answer on. - Options: to answer, for answering, to answer for, no improvement. - The priest is expected to respond directly to questions.

Concept / Approach:
In standard English, one agrees to do something, and one answers questions, not answers on questions. The usual structure is agree to answer questions. The preposition on is unnecessary directly after answer in this context, because answer takes its object without a preposition. Therefore, the most natural and correct phrase is to answer, and the full sentence should read The priest agreed to answer questions on theology.

Step-by-Step Solution:
Step 1: Identify the pattern after agreed. The verb agree is normally followed by to plus base verb when indicating a willingness to do something. Step 2: Recognise that answer already takes its object directly: answer questions, not answer on questions. Step 3: Remove the unnecessary preposition on and keep only to answer. Step 4: Insert option A into the sentence: The priest agreed to answer questions on theology. Step 5: Confirm that this new sentence is grammatical and sounds natural in formal English.

Verification / Alternative check:
Test the other options briefly. For answering would normally be used after a different structure, such as was responsible for answering or thanked him for answering, not directly after agreed. To answer for implies being responsible for or having to justify something, for example answer for his actions, which changes the meaning entirely. No improvement would keep the original to answer on, which is non standard. This comparison strengthens the choice of to answer.

Why Other Options Are Wrong:
Option B, for answering, does not follow agreed in a natural way and breaks the pattern agree to do something. Option C, to answer for, introduces the phrasal verb answer for, which usually means to take responsibility for something negative, not to respond to questions. Option D, no improvement, would keep the incorrect phrase to answer on and ignore the needed simplification. None of these options match the basic grammar reflected in agree to answer questions.

Common Pitfalls:
Students sometimes add unnecessary prepositions after verbs that already take direct objects, especially when they are influenced by similar patterns in their first language. Another frequent error is to treat agree to and answer on as a single combined phrase, when in reality agree and answer follow different patterns. A helpful practice is to learn common verb plus infinitive combinations like agree to help, decide to go, and promise to answer, and then apply them consistently.

Final Answer:
to answer is the correct improvement, giving the sentence The priest agreed to answer questions on theology.