Explanation:

The correct answer is option B- "mine".

Possessive Pronouns and Adjectives:
- Possessive pronouns are used to show ownership or possession.
- Possessive adjectives are used to describe who owns or possesses something.

Usage of "mine":
- "Mine" is a possessive pronoun that is used to show ownership or possession.
- It is used when we want to emphasize that something belongs to the speaker.

Example:
- This book is mine. (Here, "mine" shows that the book belongs to the speaker.)

Usage of "my":
- "My" is a possessive adjective that is used to describe something that belongs to the speaker.
- It is followed by a noun.

Example:
- That is my car. (Here, "my" describes that the car belongs to the speaker.)

Explanation of the given sentence:
- The given sentence is "That policeman is a friend of _____"
- We need to fill the blank with a possessive pronoun or adjective that shows ownership or possession of the policeman's friend.

Reasoning:
- Since we are talking about the policeman's friend, we need to use a possessive pronoun or adjective that refers to the friend.
- The options "my" and "me" both refer to the speaker, not the friend.
- Therefore, the correct answer is option B- "mine", which shows ownership or possession and refers to the speaker's friend.

Final Answer:
- The correct answer is option B- "mine".

Explanation:
The correct answer is option 'B' - mine.

Understanding the sentence:
The sentence states that the policeman is a friend of someone. We need to determine the appropriate possessive pronoun or adjective to complete the sentence.

Possessive pronouns:
Possessive pronouns are used to show ownership or possession of something. They replace the noun and act as adjectives. The possessive pronouns are: mine, yours, his, hers, its, ours, and theirs.

Using possessive pronouns:
We use possessive pronouns to show that something belongs to someone. In this case, the sentence is referring to the policeman being a friend of someone. To indicate that the policeman is a friend of the speaker, we need to use the possessive pronoun "mine."

Using possessive adjectives:
Possessive adjectives are used to describe the noun and show ownership or possession. The possessive adjectives are: my, your, his, her, its, our, and their.

Why possessive adjective is not the correct answer:
In this sentence, we are not describing the noun "friend" but indicating the ownership or possession of the friend. Therefore, we cannot use the possessive adjective "my" because it does not show ownership or possession. Instead, we need to use the possessive pronoun "mine."

Example:
If the sentence were "That policeman is a friend of my brother," then the correct answer would be "my" as we are describing the noun "brother."

Conclusion:
In conclusion, we use the possessive pronoun "mine" in this sentence to indicate that the policeman is a friend of the speaker. Therefore, the correct answer is option 'B' - mine.