Vanguard' (called 'हरावल दस्ता' in Hindi) refers to the forward or leading part of an army that advances first into battle, ahead of the main forces. So the correct answer is Front of the army, option (1).
PRO TIP
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Related Questions
A circuit has a battery, a bulb and two electrodes dipped in a beaker. The bulb glows when the beaker contains: