In this voice transformation question, convert the sentence "Dark clouds have overcast the evening sky." into the correct passive voice form by selecting the appropriate option.

Introduction / Context:
This question checks your understanding of active and passive voice transformation in English grammar. You are given an active voice sentence, "Dark clouds have overcast the evening sky", and asked to choose the correct passive voice version. Mastery of tense, verb form, and correct word order is essential to solve such questions accurately.

Given Data / Assumptions:

• Active sentence: "Dark clouds have overcast the evening sky."
• Subject in active voice: "Dark clouds".
• Object in active voice: "the evening sky".
• Main verb phrase: "have overcast" (present perfect tense).
• We must convert to passive voice while keeping the same tense and basic meaning.

Concept / Approach:
In voice transformation, the object of the active sentence becomes the subject of the passive sentence. The tense of the main verb must remain the same. For present perfect tense, the passive structure is: has/have been + past participle. The verb "overcast" has the same form as base and past participle; it does not become "overcastted". We also usually introduce the doer with "by" if it is mentioned. Therefore, we are looking for a sentence that begins with "The evening sky" and uses "has been overcast by the dark clouds".

Step-by-Step Solution:
Step 1: Identify subject, verb, and object in the active sentence: Subject "Dark clouds", verb "have overcast", object "the evening sky". Step 2: In the passive form, move the object to the subject position: "The evening sky". Step 3: Maintain present perfect tense by using "has been" plus the past participle. Since "the evening sky" is singular, we use "has been". Step 4: Use the correct past participle. The verb "overcast" remains "overcast" in past participle, so we write "has been overcast". Step 5: Add the agent phrase with "by": "by the dark clouds". The full passive sentence becomes "The evening sky has been overcast by the dark clouds."

Verification / Alternative check:
Examine each option. Option B reads "The evening sky has been overcast by the dark clouds." It matches our constructed passive form exactly. Option A, "By the dark clouds the evening sky was overcast", changes the tense to simple past ("was overcast") and uses an unusual word order. Option C, "Dark clouds overcastted the evening sky", remains in active voice and uses an incorrect verb form. Option D, "The sky of the evening was overcasted by dark clouds", uses the wrong tense and the non standard form "overcasted". Only option B preserves tense, meaning, and correct verb form.

Why Other Options Are Wrong:
Option A shifts the tense from present perfect ("have overcast") to simple past ("was overcast") and uses awkward inversion by starting with "By the dark clouds".

Option C does not convert to passive at all, and "overcastted" is incorrect; the verb "overcast" does not take "ed".

Option D also uses "overcasted", which is not accepted in standard English, and changes the tense to simple past, along with an unnatural phrase "the sky of the evening".

Common Pitfalls:
A frequent mistake is to change the tense unintentionally while converting active to passive. Another common error is to add "ed" to verbs that already have irregular past participle forms, as in "overcasted". To avoid such errors, always identify the tense first, recall the correct passive pattern for that tense, and check the dictionary form of any irregular verbs. For present perfect, the pattern is "has/have been + past participle".

Final Answer:
The correct passive voice sentence is "The evening sky has been overcast by the dark clouds."