Su Jiu softly said, "Daddy, you're wrong."
Su Shengjing frowned. "How can it be wrong? Darling, look. It's obvious that it's a river. It can flow through anything smoothly, but only downstream due to gravity. The answer should be the river."
When he said that, the audience understood it. So that's the answer to the riddle!
As "R" was the first letter of the river, Su Shengjing thought it was the password.
"How impressive! His logical reasoning is quite good. It's quite amazing that he managed to think of that."
"Oh my god, I didn't think of that at all! His explanation sounds reasonable, so why was it wrong?"
Su Shengjing glanced at the innocent little girl in his arms and smiled. "Darling, can you understand what I'm saying?"
Of course I can!
Su Jiu mumbled in her heart. However, she tilted her head and pretended to think. Suddenly, her eyes lit up, and she said, "Daddy, I know!"