Spot the Error in the sentence: A year has gone by/since he left us/a…

The correct answer is Option (3) → (C) Only

Present perfect with "since":

• An action or state that started in the past and continues up to now takes the present perfect (has / have + past participle).
• "Since + a point in past time" marks where that period began.
• This sentence: the time frame "A year has gone by since he left us" runs up to now, so the second action must be in the present perfect too: "and we have never heard any news of him".
  Example: It is two years since we moved here, and we have never had a power cut.

(A) A year has gone by — No error.

• The present perfect has gone by covers the period up to now.

(B) since he left us — No error.

• Since is followed by the simple past for the point at which the period began.

(C) and we never hear — Error.

• The simple present "hear" describes a habit.
• It should be "and we have never heard", for the whole period since he left.
• Correct form: A year has gone by since he left us and we have never heard any news of him.

(D) any news of him. — No error.

• "News of someone" is correct.