Explanation:

- The given sentence describes an attempt that took place in the past, and what was discovered at that time about the phone’s status.

- Option 1: No improvement

- The original phrase "appeared to have been" properly indicates the past status of the phone.

- It is suitable as it reflects the completion of an action (the phone being switched off) before or by the time of another past action (trying to contact).

- Option 2: Appears to had been

- "Appears" is present tense, which contradicts the past context indicated by "tried."

- "Had been" does not fit because it suggests a past perfect action without a past simple anchor.

- Option 3: Appeared to been

- This is grammatically incorrect. "Been" requires forms of "have" to establish a tense.

- Option 4: Appear to be

- This is present tense, which does not agree with the past action in the sentence.