Spoil the Monk episode with the guy cheating on the game show, please

Cafe Society
1

I was half-watching the episode, so I didn’t catch how it turned out the guy was cheating. How was is done?

2

The questions were all multiple choice, and he held the answer card by the corner – upper right if the answer was a, lower right if the answer was b, etc.

3

“He” meaning the host of the show, whom the contestant was blackmailing.

4

Thanks!