Explanation:


The correct preposition to use in this sentence is "at", as it refers to a person's ability or skill in a particular area. Here is a detailed explanation:

Prepositions:


Prepositions are words that show the relationship between a noun or pronoun and other words in a sentence. They are used to indicate place, time, direction, manner, cause, and other relationships. In this sentence, the preposition "at" is used to show a person's ability or skill in making friends.

Use of "at" for skills:


The preposition "at" is commonly used to indicate a person's skill or ability in a particular area. For example:

- He is good at playing chess.
- She is skilled at public speaking.
- They are experts at solving complex problems.

Application in the given sentence:


In the given sentence, the phrase "good at making friends" indicates a person's ability or skill in making friends. Therefore, the correct preposition to use is "at."

Importance in the field of trade:


The sentence also mentions that people who are good at making friends usually work in the field of trade, which requires having good communicative skills. This means that in the field of trade, it is important to be able to establish and maintain relationships with clients, customers, and colleagues. Being good at making friends can help in building a strong network and achieving success in this field.

Conclusion:


In summary, the use of "at" in the given sentence is correct because it indicates a person's ability or skill in making friends. Additionally, the sentence highlights the importance of good communicative skills in the field of trade, where building relationships is crucial for success.