Correct Answer & Explanation
Option C
• The verb 'belong' is a stative verb, which generally does not take continuous forms.
• The phrase 'since his birth' indicates a duration leading up to a point in the past (implied by the context of a narrative or a past event, although not explicitly stated as a second past action here, the example in the source text for 'had belonged' uses this structure for past ownership).
• If the context implies this ownership was true up to a certain point in the past, Past Perfect is appropriate. The source's example 'The house had belonged to him since his birth' confirms this usage for past stative duration.