In this English grammar question, a sentence is given in active voice. Select the option that best expresses the same idea in passive voice. Sentence: "To pass, the candidate has to answer at least three questions correctly."

Introduction / Context:

This item focuses on converting an instruction in active voice into a natural passive voice sentence. The original sentence sets a condition for passing an examination, and it states that the candidate has to answer at least three questions correctly. The correct option must restate this condition in passive voice without changing the requirement.

Given Data / Assumptions:

- Original sentence: "To pass, the candidate has to answer at least three questions correctly."

- Subject in the active sentence: "the candidate".

- Object: "at least three questions".

- The action is "has to answer" which expresses obligation or necessity.

- We need a passive form that keeps the sense of obligation and the condition for passing the examination.

Concept / Approach:

When we change a sentence with obligation, such as "has to answer", into passive voice, the object of the active sentence moves into the subject position. The pattern usually becomes "have to be answered" or "must be answered" plus the agent phrase if it is needed. The meaning must remain that answering at least three questions correctly is required in order to pass. We must avoid changes that turn the sentence into a simple prediction or into a different tense.

Step-by-Step Solution:
Step 1: Identify the subject, verb, and object. Subject: the candidate. Object: at least three questions. Verb phrase: has to answer. Step 2: Move the object "at least three questions" to the subject position in the passive sentence. Step 3: Create a passive verb phrase that expresses necessity, such as "must be answered" or "have to be answered". Step 4: Add the agent phrase "by the candidate" to show who must perform the action. Step 5: Keep the phrase "in order to pass" or an equivalent expression, so the condition remains clear.

Verification / Alternative check:

The sentence "At least three questions must be answered correctly by the candidate in order to pass." keeps the same meaning as the original. It clearly shows that a minimum of three correct answers is a requirement for passing, and it uses a natural passive pattern. The obligation is present in the phrase "must be answered", which matches the strength of "has to answer".

Why Other Options Are Wrong:

Some options keep the sentence in active voice and simply rephrase the condition, which does not meet the requirement to use passive voice. Other choices distort the grammar by using incorrect word order or by combining verbs in a way that native speakers would not accept. A few options mix up the tense or fail to mention that the answers must be correct, which weakens or changes the original condition. Because of these issues, those sentences are not suitable passive voice equivalents.

Common Pitfalls:

Many learners confuse sentences of obligation with simple statements of fact and forget to keep the required sense of necessity. When changing to passive voice, it is easy to drop important words like "correctly" or "at least", which alters the exam rule. Another common mistake is to produce clumsy constructions such as "answering is done by the candidate", which sound unnatural and are rarely used in formal English. Careful checking of meaning, tense, and word order helps avoid these errors.

Final Answer:

The correct passive voice sentence is "At least three questions must be answered correctly by the candidate in order to pass."