Infinity Challenge, 1N2D, and Running Man casts exempt from the military

Infinity Challenge

Park Myung Soo - eyesight
Jung Junha - the only son of fourth generation

1N2D

Cha Tae Hyun - habitual shoulder dislocation
Jung Joon Young - no educational background 
(his education background was not confirmed because he lived overseas all along)

Running Man

Song Jihyo - ???

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Instiz: Infinity Challenge, 1N2D, and Running Man members that were exempt from the military service

- What's the only son of fourth generation?
-- It means that Jung Junha's family had only one child in each generation and they were all sons. He's the fourth. This used to get people exempt from the military but not anymore.
- Your great-grandfather is the only son of the family, your grandfather is the only son of the family, your father is the only son of the family, and you're the only son of your family. You then get exempt. It doesn't work anymore.

- Song Jihyo ㅋㅋㅋㅋㅋ

- Woah, if Jung Junha keeps his current son and doesn't have a second child, the son will be the only son of fifth generation ㅋㅋㅋ

- No education background is also a reason...?