In a four stroke cycle petrol engine, the charge is ignited at

• A. 30¬¨¬®‚Äö√†√ª after bottom dead centre
• B. 30¬¨¬®‚Äö√†√ª before bottom dead centre
• C. 30¬¨¬®‚Äö√†√ª after top dead centre
• D. 30¬¨¬®‚Äö√†√ª before top dead centre