The correct passive form of the given sentence is:

☀ The plane was landed safely by the pilot.

Let's break down the options:

1. The plane had been landed safely by the pilot. (Incorrect) This option uses the past perfect tense "had been landed," which implies that the landing happened before some other past event. The original sentence is in the simple past tense, so option 2 is the correct choice.

2. The plane was landed safely by the pilot. (Correct) This sentence correctly uses the passive voice and conveys the same meaning as the original sentence.

3. The plane has been landed safely by the pilot. (Incorrect) This option uses the present perfect tense "has been landed," which implies that the landing happened in the past with present relevance. The original sentence is in the simple past tense, so option 2 better reflects the intended meaning.

4. The plane was to be landed safely by the pilot. (Incorrect) This option introduces "to be" in the passive construction, suggesting a future intent to land the plane. The original sentence is in the past tense, not the future, so option 2 is the correct choice.