The phrase: How can you tell?

English as a Second Language English Vocabulary, Grammar and Idioms
1

What does the phare ‘how can you tell’ mean in this conversation:
A: I thought he was a liar.
B: No, He’s a good guy.
A: Well, how can you tell?

Please help me, thank you?

2

It means “why”

3

It means “why”.

4

It doesn’t mean ‘why?’
It means ‘How do you know that he is a liar?’

5

thank you Beeesneees, I get it!

6

thank you!Dear,my professor.