India is known for her diversity, although in the face of any external threat all Indians unite to fight her common enemy. This inter group conflict, which finally becomes intergroup cooperation because of:-

focusing on superordinate goals

The correct answer is Option (1) → focusing on superordinate goals

A superordinate goal is a shared goal that can only be achieved through the cooperation of all groups, regardless of their individual differences. When India faces an external threat, diverse communities and groups come together, setting aside their differences, to protect the nation—a common goal that unites them.

The other options are incorrect:

• Intergroup competition would exacerbate conflict, not resolve it.
   
• In-group formation is part of the problem, as it's the initial division into groups that creates the conflict.
• Friends among foes might help on a small scale, but it's not the primary reason for large-scale intergroup cooperation in the face of an external threat.

Note: This is a question from Pre-rationalised NCERT textbook.