Change the sentence from Active to Passive voice: The seawater eventually corroded the pillars of the bridge.

Introduction / Context:
This question tests your understanding of voice transformation, a standard topic in English grammar. The original sentence is in the Active voice and uses the simple past tense. Your task is to select the option that correctly changes it into the Passive voice while preserving both the tense and the meaning. Knowing how to change the subject, object, and verb form is essential for this type of question.

Given Data / Assumptions:

• Active sentence: The seawater eventually corroded the pillars of the bridge.
• Subject: the seawater.
• Object: the pillars of the bridge.
• Tense: simple past (corroded).
• We must form the passive with the object as subject and use correct past passive verb form.

Concept / Approach:
In transforming from Active to Passive voice, the object of the active sentence becomes the subject of the passive sentence, the subject of the active sentence is introduced by by, and the verb changes to a form of be plus the past participle. Since the original verb is in simple past (corroded), the passive should use was or were plus corroded. The adverb eventually should be placed so that the sentence remains natural and clear.

Step-by-Step Solution:
Step 1: Identify object in the active sentence: the pillars of the bridge. Step 2: Bring this object to the subject position in the passive: The pillars of the bridge ... Step 3: Change simple past active corroded to simple past passive were corroded, because pillars is plural. Step 4: Add the agent with by: by the seawater. Step 5: Place the adverb eventually in a natural position: The pillars of the bridge were eventually corroded by the seawater. Step 6: Compare this result with the options and match it to option c.
Verification / Alternative check:
Check the tense and structure. The original focuses on the action done by seawater in the past. In the passive, the focus shifts to the pillars, but the time reference remains in the past through were corroded. The adverb eventually can come before or after the verb, but The pillars of the bridge were eventually corroded by the seawater is both grammatically correct and stylistically natural. This confirms option c as correct.

Why Other Options Are Wrong:

• Option a: are being corroded is present continuous passive, which changes the tense and meaning.
• Option b: have been corroded is present perfect passive, again changing the tense from simple past to present perfect.
• Option d: have been eventually corroded is also present perfect, and the placement of eventually is awkward.

Common Pitfalls:
A common mistake is to forget that the tense must remain the same when changing voice. Many learners focus on forming a correct passive structure but accidentally change simple past into present perfect or continuous. Another pitfall is misplacing adverbs like eventually, which can make the sentence sound unnatural even if the tense is correct. Always confirm that you have used was or were plus the past participle for simple past passive and that the sentence sounds smooth when spoken aloud.

Final Answer:
The correct passive form is The pillars of the bridge were eventually corroded by the seawater.