Posthumous works create a timing problem for copyright law, since the author is no longer alive to see the work published, the law has to pick some other fixed point from which the protection period runs, and that point has to be defined clearly enough that everyone can calculate it with certainty.
Section 24 solves this by anchoring the term to first publication rather than to death, giving the posthumous work its own sixty year window measured from the start of the calendar year after it is first published. This is exactly what Statement I describes, so it stands correct.
Once the term depends on the date of first publication, the law needs to say precisely what counts as publishing a work, otherwise the sixty year clock could never be set with confidence. The Act answers this by treating publication as making the work available to the public, whether through issuing copies of it or through communicating it to the public. This is exactly what Statement II describes, and it too is correct.
Because the second definition exists specifically to make the first rule workable, the two statements are not competing ideas but two connected parts of the same rule, and both hold true together.
So the correct reading is that both statements accurately state the law.
\[ \boxed{\text{Both Statements I and II are true}} \]