Is radio a open syllable?

Yes!

Explanation:

Because an open syllable ends with a vowel sound that is spelled with a single vowel letter (a, e, i, o, or u).

be more specific with your question.

faithful servants eumaeus and philaetius:

his ragged vest then drawn aside disclosed the sign conspicuous, and the scar exposed: eager they view'd, with joy they stood amazed with tearful eyes o'er all their master gazed:

these servants know ulysses by the scar he got when he was a child - so when he showed them the mark, they immediately knew this is truly their master and they hugged him, finally starting to believe his words.