The passage mainly explains

how a stone with matching texts let scholars finally read hieroglyphs (The passage tells how three matching texts, one in readable Greek, allowed hieroglyphs to be decoded.)

What made the stone useful for decoding hieroglyphs?

All three blocks said the same thing, one in readable Greek (The text says all three said the same thing, and one block was in Greek that scholars could read.)

The passage calls the stone 'ordinary' to make the point that

its worth came from the matching writing, not the rock itself (It says 'its power lay in the match between its three texts'; the method, not the material, mattered.)

In this passage, 'scripts' most nearly means

systems of writing (Set against 'a language' in the next sentence, 'scripts' means systems of writing.)

Cracking the Rosetta Stone: Level 3 Reading Comprehension Questions

For centuries, the picture-writing of ancient Egypt was a locked door. The symbols, called hieroglyphs, covered temple walls and tombs, but no one alive could read them. Their meaning had been forgotten for more than a thousand years.

The key turned up by accident. Soldiers digging near the Egyptian town of Rosetta uncovered a slab of dark stone carved with three blocks of writing. Scholars soon realized that all three said the same thing, but in three different scripts. One block was written in Greek, a language scholars still understood. If the three texts matched, then the Greek could serve as a translation of the other two.

Even so, the puzzle took years. Comparing the scripts letter by letter, scholars slowly worked out which symbols stood for sounds and which stood for ideas. A young French scholar finally pieced the system together, and the locked door swung open. Suddenly the writing on thousands of monuments could speak again, and a lost world of kings, gods, and daily life came back into view. The stone itself was ordinary; its power lay in the match between its three texts.

Comprehension questions