What does a readability of 2 indicate?

Question

Quiz SPL - Sailplane Pilot License - Communication - What does a readability of 2 indicate?

QuizVDS · Accepted Answer

The transmission is readable now and then

QuizVDS · Answer

The transmission is readable but with difficulty

QuizVDS · Answer

The transmission is unreadable

QuizVDS · Answer

The transmission is perfectly readable

SPL: What does a readability of 2 indicate?