Fill in the blank with the correct preposition: "He was sworn _____ as the Prime Minister of our country."

Introduction / Context:
This question tests knowledge of fixed expressions in English, especially those used in political and ceremonial contexts. When a person assumes a formal office, such as President, Prime Minister, or judge, English uses a specific phrasal verb with sworn. Knowing this phrase is essential for understanding news reports and official statements about changes in government or leadership.

Given Data / Assumptions:

• Sentence: He was sworn _____ as the Prime Minister of our country.
• The blank is followed by as the Prime Minister of our country.
• Four prepositions are offered: in, off, about, it.
• The context is an official oath taking ceremony.

Concept / Approach:
The correct collocation in English is sworn in as, which means formally installed into an office by taking an oath. For example, a leader is sworn in as President, or a judge is sworn in as a member of the court. The preposition in is a fixed part of this phrase. Sworn off has a completely different meaning related to giving up a habit, while sworn about and sworn it do not form any standard expression with this sense.

Step-by-Step Solution:
Step 1: Recognise that sworn is used here in a passive construction describing a ceremony. Step 2: Recall the common phrase sworn in as used in political news and official reports. Step 3: Insert in into the sentence: He was sworn in as the Prime Minister of our country. Step 4: Check that the resulting sentence reads smoothly and matches typical usage. Step 5: Eliminate other prepositions that do not create meaningful or idiomatic combinations.

Verification / Alternative check:
Think of similar expressions: The new cabinet was sworn in yesterday. He was sworn in as the chief minister. In all such cases, in is used after sworn to indicate formal assumption of duties. Sworn off would appear in sentences like He has sworn off sweets, which clearly belong to a different semantic field. Since our sentence refers to appointment as Prime Minister, only sworn in as is appropriate.

Why Other Options Are Wrong:
Off changes the meaning to giving up something, as in sworn off smoking, which is unrelated to official appointments.

About does not combine with sworn to form any idiomatic phrase in this context, and sworn about as the Prime Minister is ungrammatical.

It is not a preposition and simply does not fit structurally after sworn in the sentence.

Common Pitfalls:
Some learners confuse this expression with sworn to, which appears in contexts like sworn to secrecy. They may then try to use to after sworn in this sentence. Remember that sworn in as is used when someone takes office, while sworn to secrecy or sworn to protect refers to promises or duties. Keeping these contexts separate will help you choose the correct preposition quickly in exams.

Final Answer:
The correct preposition is in, giving He was sworn in as the Prime Minister of our country.