Sheikh Mujeeb-ur-Rehman met his end by

Sheikh Mujeeb-ur-Rehman, the revered founding father of Bangladesh and its first President, met a tragic end not by natural causes or accident, but through a deliberate act of violence. This event is historically recognized as an assassination.

• Correct Option B: Assassination is accurate because he was brutally murdered along with most of his family members by a group of disgruntled junior army officers during a military coup on August 15, 1975. This was a planned political killing.
• Option A: Accident is incorrect as his death was a premeditated act, not an unforeseen mishap.
• Option C: Heart failure is incorrect as his death resulted from gunshot wounds, not a medical condition.
• Option D: None is incorrect as 'Assassination' precisely describes the manner of his death.