When is "Have you known" correct?
We usually say:
Did you know that penguins can't fly, although they are classified as "birds"?
But, when "Have you known" is grammactly correct?
Solution 1:
"How long have you known that penguins can't fly?"
The present perfect tense draws attention to the circumstance after the action is complete. The interrogative "how long" sounds natural with a present perfect.