Answer: Option A
In the given sentence, "dispensed with" means to do away with or get rid of something, and "services" refer to the work or duties performed by the clerk. The sentence means that "he got rid of the work or duties performed by his dishonest clerk."
The preposition "of" is used to show possession, origin, or association. In this case, "of" is used to show possession of the services by the clerk. Therefore, the correct preposition to use is "of".
Let's consider the other options and see why they are incorrect:

• B. "by" - This preposition is used to indicate the agent of an action or the means of achieving something. It does not fit the context of the sentence because the clerk is not the agent of the action; rather, he is the object of the action.
• C. "for" - This preposition is used to indicate the purpose of an action or the person or thing that benefits from an action. It does not fit the context of the sentence because the clerk is not the person who benefits from the action; rather, he is the person who is being dispensed with.
• D. "to" - This preposition is used to indicate the recipient of an action. It does not fit the context of the sentence because the clerk is not the recipient of the action; rather, he is the person who is being dispensed with.
• E. "from" - This preposition is used to indicate the source or origin of something. It does not fit the context of the sentence because the clerk is not the source or origin of the services; rather, he is the person who performs them.

In summary, the correct preposition to use in the given sentence is "of" because it shows the possession of the services by the clerk.
Formula/Definition:

• Prepositions are words that show the relationship between a noun or pronoun and other words in a sentence.
• "Of" is a preposition that indicates possession or association between two nouns or pronouns.
• "Dispense with" means to do away with or get rid of something or someone.