Identify the suitable modals which indicate 'some kind of rule' in the following sentence.
'In Delhi even the pillion-riders ________ wear a helmet.'

The correct answer is Option B (have to).

Key Points:
• Concept: Expressing external rules or legal obligations using Modals. 'Have to' is primarily used to express external obligation imposed by rules, laws, or authority.
• Explanation:
• Subject: 'pillion-riders' (Plural subject).
• Rule/Obligation: Expressed by 'have to' for plural subjects.
• 'In Delhi even the pillion-riders have to wear a helmet.'
• Other Options: 'has to' is singular; 'must' indicates personal obligation or strong necessity, but 'have to' specifically denotes external rules/laws.
• Official Key: Option 2 ('have to') is the official answer declared in the MPSC Final Answer Key.
• Key Takeaway: Remember: 'Have to' is used to denote external obligations imposed by legal rules and regulations.